# n a study using 15 respondents and in which the population variance is unknown, what distribution should be used to calculate the confidence interval

100,104 results

1. ### stats

n a study using 15 respondents and in which the population variance is unknown, what distribution should be used to calculate the confidence interval.
2. ### statistics

Consider the data from an unknown distribution: 40.68, 32.15, 36.91, 29.00, 35.58, 41.55, 33.83, 29.07, 41.00, 37.68, 41.23, 37.54, 40.33, 36.82, 35.18, 31.67, 38.55, 38.34, 35.86, 40.45, 37.28, 36.65, 32.12, 32.96, 37.65, 39.44, 46.18, 24.21, 42.35, 33.05, 30.90, 42.12, 34.38...
3. ### res342

In conducting research that looks at differences in populations, samples are used for numerous reasons. Using entire populations in a test is difficult, so various sampling techniques are applied. In situations in which the population variance is unknown, the Student t ...
4. ### Statistics

Which of the following statements correctly interprets a 95% confidence interval on a population mean? a. It is a single point estimate b. Used to quantify the certainty of the sample standard deviation c. A 99% confidence interval is narrower than the 95% confidence interval ...
5. ### Statistics

Which of the following statements best describes the uncertainty associated with a 95% confidence interval for a population proportion, computed from a simple random sample? A. We don't know whether the particular confidence interval is successful or not, but 95% of ...
6. ### Statistics

Suppose x has a mound-shaped distribution with sigma = 9 . A random sample of size 36 has sample mean 20. Is it appropriate to use a normal distribution to compute a confidence interval for the population mean m? Explain. Find a 95% confidence interval for m. Explain the ...
7. ### statistics

For a sample size of 10 from a population whose standard deviation is not known, which type of probability distribution is used to help calculate a confidence interval for the mean?
8. ### math

With a confidence level of .95 and a confident interval of 5 and a population of 20,000 what is the sample size? With a confidence level of .99 and a confident interval of 5 and a population of 20,000 what is the sample size? Finally, using the sample size for question 1 and 2...
9. ### statistics

Suppose we take a random sample of size n from a normal population with variance, σ2 . It can be shown that (n−1)s2/σ2 has a chi-square distribution with n−1 degrees of freedom, where s is the sample variance. Below is a random sample of size 8 drawn from...
10. ### Statistics

The grades in the final exam of a random sample of 25 students produce a standard deviation, s = 9.5. a) Construct a 90% confidence interval estimate for the population variance, . b) Can we infer at 10% level of significance that the population variance is significantly ...
11. ### Statistics

Suppose you have a sample of 6 observations from a normal population. The sample variance is equal to 4. Find a 90% lower confidence interval for the variance of the population.
12. ### Statistics

1. A certain population follows a normal distribution, with mean m and standard deviation s = 2.5. You collect data and test the hypotheses H0: m = 1, Ha: m 1. You obtain a P-value of 0.022. Which of the following is true? Why? a. A 95% confidence interval for m will include ...
13. ### statistics

Lorraine was in a hurry when she computed a confidence interval for μ. Because σ was not known, she used a Student's t distribution. However, she accidentally used degrees of freedom n instead of n - 1. Will her confidence interval be longer or shorter than one found...
14. ### Statistics

You are given the following information obtained from a random sample of 6 observations. Assume the population has a normal distribution. 13 14 17 14 17 15 a. What is the point estimate of µ? b. Construct an 80% confidence interval for µ. c. Construct a 98% confidence ...
15. ### statistics

Consider a 95% confidence interval for a population mean constructed from a random sample of 250 observations taken from a Normal population. Sigma is known to be 14. If we were to construct another 95% confidence interval, this time using 1,000 observations, how would the ...
16. ### statistics

Consider a 95% confidence interval for a population mean constructed from a random sample of 250 observations taken from a Normal population. Sigma is known to be 14. If we were to construct another 95% confidence interval, this time using 1,000 observations, how would the ...
17. ### Statistics

The standard deviation for a population is σ = 15.3. A sample of 36 observations selected from this population gave a mean equal to 74.8. a) Make a 90% confidence interval for μ b) Construct a 95% confidence interval for μ. c) Determine a 99% confidence interval...
18. ### Statistics

Can anyone help me with this? Which of the following statements is true about a 99% confidence interval? a. The interval contains 99% of the population. b. The probability that the population mean is in the interval is 99%. c. The interval is wider than a 95% confidence ...
19. ### stats

4. Data from the 2008 General Social Survey (GSS) sample show that the mean number of children per respondent was 1.94 with a standard deviation of 1.70. A total of 2,020 people answered this question. (a) Estimate the population mean number of children per adult using a 90% ...
20. ### Statistics

In 1998 a San Diego Reproductive clinic reported 49 live births to 207 women under the age of 40 who had previously been unable to get pregnant. Using the 90% confidence interval calculated above, would it be misleading for the clinic to report a success rate of 25%? A) Yes, ...
21. ### STAT

1. In a study of the income of U.S. factory workers, a random sample of 100 workers shows a sample mean of \$35,000. Assume that the population standard deviation is \$4,500, and that the population is normally distributed. A) Compute the 90%, 95% and 99% confidence intervals ...
22. ### statistics

Lorraine was in a hurry when she computed a confidence interval for . Because was not known, she used a Student's t distribution. However, she accidentally used degrees of freedom n + 1 instead of n - 1. v Will her confidence interval be longer or shorter than one found using ...
23. ### statistikc

We want a confidence interval for the mean IQ of all the 7th grade girls in that school district. We do not know the population standard deviation so we use the confidence interval that uses the t. In order to use the t-interval we need to assume that the variable IQ has a ...
24. ### statistics

You intend to estimate a population proportion with a confidence interval. The data suggests that the normal distribution is a reasonable approximation for the binomial distribution in this case. While it is an uncommon confidence level, find the critical value that ...
25. ### Statistics

In a study to estimate a population mean, i start with a sample size 10 and calculate the 95% confidence interval. Suppose i am not satisfied with the size of the confidence interval and want to reduce it by half. Give an estimate of sample size that i need.
26. ### Statistics

The population standard deviation is estimated to be \$300. If a 98% confidence interval is used and an interval of +/-\$75 is desired, how many cardholders should be sampled?
27. ### stats

1. A confidence interval can be calculated to estimate the population mean when the population is normally distributed or the sample size is greater than 30. Can a confidence interval be calculated for the average number of hours of sleep for the US babies using this ...
28. ### statistics

A psychologist wants to estimate the variance of employee test scores. A random sample of 18 scores had a sample standard deviation 10.4. Find a 90% confidence 2 interval for the population variance. What assumption, if any, have you made in calculating this interval estimate?
29. ### Statistics

Multiple Choice Which of the following statements is true about the 95% confidence interval of the average of a sample? A) 95 of 100 avgs of samples will be within the limits of the confidence interval. B) There is a 95% chance the avg of the population to be within the limits...
30. ### statistics

Use the given confidence level and sample data to find a confidence interval for the population standard sigma. Assume that a simple random sample has been selected from a population that has a normal distribution. salaries of college graduates who took a geology course in ...
31. ### math

A class survey in a large class for first-year college students asked, “About how many minutes do you study on a typical weeknight?” The mean response of the 463 students was = 118 minutes. Suppose that we know that the study time follows a Normal distribution with ...
32. ### statistics

Prospective Cohort Study The following tables show the crude and sex-specific results from a Prospective Cohort Study that examines the association between a binary exposure (E) and the development of a disease (D) during 20 years of follow-up. Full Data: Sex-Specific Data: ...
33. ### Math

A study of generator related carbon monoxide deaths showed that a sample of 6 recent years had a variance of 16.8 deaths per year. Find the 99% confidence interval of the true variance
34. ### Statistics

A study of generator related carbon monoxide deaths showed that a sample of 6 recent years had a variance of 16.8 deaths per year. Find the 99% confidence interval of the true variance
35. ### Statistics

You are interested in estimating the mean of a population. you plan to take a random sample from the population and use the samples mean as an estimate of population mean. Assuming that the population from which you select your sample is normal, which of the statements about ...
36. ### Statistics

The confidence interval below for the population variance is based on the following sample statistics: n = 25, x-bar = 31.1, and s = 4.2. 9.29 < standard deviation squared < 42.82 What is the degree of confidence?
37. ### statistics

You intend to estimate a population proportion with a confidence interval. The data suggests that the normal distribution is a reasonable approximation for the binomial distribution in this case. Find the critical value that corresponds to a confidence level of 98%. (Report ...
38. ### stat math

Stat hw question help me please? In a high profile murder case a sample of the general public's opinions concerning the guilt or innocence of the defendant is taken. A sample of n=100 males results in 62% of the respondents beliving that the defendant is guilty, while a sample...
39. ### probs & stats

1. A study of 40 people found that they could do on the average15 pull ups with a standard deviation of .6. Find the 99% confidence interval for the mean of the population. 2. A study of 50 pizza delivery workers found that they could make 6 deliveries per hour with a standard...
40. ### Statistics

1. A study of 40 people found that they could do on the average15 pull ups with a standard deviation of .6. Find the 99% confidence interval for the mean of the population. 2. A study of 50 pizza delivery workers found that they could make 6 deliveries per hour with a standard...
41. ### Statistics

1. A study of 40 people found that they could do on the average15 pull ups with a standard deviation of .6. Find the 99% confidence interval for the mean of the population. 2. A study of 50 pizza delivery workers found that they could make 6 deliveries per hour with a standard...
42. ### Statistics:Z and T Statistics: Confidence Interva

Z and T Statistics: Confidence Intervals and Significance Tests: A friend who hears that you are taking a statistics course asks for help with a specific chemistry lab report. She has made four independent measurements of the specific gravity of a compound. The results are : 4...
43. ### Elementary Statistics

1) Construct a confidence interval of the population proportion at the given level of confidence. x=60,n=300, 99% confidence. The 99% confidence interval is (_,_) 2) A researcher wishes to estimate the proportion of adults who have high-speed internet access. What size sample ...
44. ### statistics

An experiment was conducted to determine the abrasion resistance of a new type of automobile paint. Twelve different strips of metal were painted with the new paint. The abrasion resistance of each piece was then tested on a machine. In the sample, the abrasion resistance ...
45. ### Statistics

Prospective Cohort Study The following tables show the crude and sex-specific results from a Prospective Cohort Study that examines the association between a binary exposure (E) and the development of a disease (D) during 20 years of follow-up. Use these data to solve the ...
46. ### Math Statistics

5. Students in an introductory statistics class were asked to report the age of their mothers when they were born. Summary statistics include Sample size: 36 students Sample mean: 29.643 years Sample standard deviation: 4.564 years a. Calculate the standard error of this ...
47. ### statistics

A film alliance used a random sample of 50 U.S. citizens to estimate that the typical American spent 78 hours watching videos and DVDs last year. The standard deviation of this sample was 9 hours. (a) Develop a 95 percent confidence interval for the population mean number of ...
48. ### statistics

Build a 95% confidence interval for the mean of the population from the given sample data. Assume that the population has a normal distribution. 16.4, 15.7, 16.2, 15.8 17.1 15.8, 15.9, 16.0, 16.4 15.0
49. ### Statistics

The t distribution should be used when ___. the sampling population is not normal the sampling population is unimodal The sampling distribution is normal and the population standard deviation is unknown the population standard deviation is known
50. ### Statistics (46)

The 2003 Statistical Abstract of the United States reported the percentage of people 18 years of age and older who smoke. Suppose that a study designed to collect new data on smokers and nonsmokers uses a preliminary estimate of the proportion who smoke of .30. a. How large a ...
51. ### Economics (45)

The 2003 Statistical Abstract of the United States reported the percentage of people 18 years of age and older who smoke. Suppose that a study designed to collect new data on smokers and nonsmokers uses a preliminary estimate of the proportion who smoke of .30. a. How large a ...
52. ### statistics

The 2003 Statistical Abstract of the United States reported the percentage of people 18 years of age and older who smoke. Suppose that a study designed to collect new data on smokers and nonsmokers uses a preliminary estimate of the proportion who smoke of .32. a. How large a ...
53. ### Statistics

When consumers apply for credit, their credit is rated using the FICO score. A bank manager used a random sample of the credit scores of 18 customers and determined the following 95% confidence interval: (613.6, 708.0) If the sample used 45 customers rather than 18 customers, ...
54. ### statistics

Help!!!!!! A confidence interval estimate for the population mean is given to be (39,90, 48.11) If the standard deviation is 11.473 and the sample size is 52 determine the maximum error of the estimate. determine the confidence level used for the given confidence interval
55. ### Statistics

We have calculated a 95% confidence interval for a proportion and would prefer the confidence interval to be more precise, that is narrower. Using the same sample, we can narrow the confidence interval using which of the following? A) increasing the confidence level B) ...
56. ### STATISTIC

A study based on a sample of size 25 reported a mean of 94 with a margin of error of 15 for 95% confidence (a) Give the 95% confidence interval. (__________,________) (b) If you wanted 99% confidence for the same study, would your margin of error be greater than, equal to, or ...
57. ### statistics

A 99% confidence interval for population variance is being formulated based on a sample of 16 observations. What are appropriate values for X^2
58. ### statistics

A 95% confidence interval for a population mean was reported to be 23,100 to 24,900. If the sample standard deviation is 5,808.26, what sample size was used in this study?
59. ### statistics

A basketball scout randomly selected 144 players and timed how long each player took to perform a certain drill. The times in this sample were distributed with a mean of 8 minutes. The population standard deviation was known to be 3 minutes. A. find the critical value for a 95...
60. ### math

A medical researcher wants to determine whether male pulse rates vary more or less than female pulse rates. Using the sample pulse rates in Data Set 1 in Appendix B, the male pulse rates can be summarized with the statistics 40=n,69.4=x,11.3=s. For females, the statistics are,...
61. ### statistics

Build a 95% confidence interval for the mean of the population from the given sample data. Assume that the population has a normal distribution. 16.4, 15.7, 16.2, 15.8 17.1 15.8, 15.9, 16.0, 16.4 15.0 *please help me solve this! I have no clue what I am supposed to do
62. ### math

A sample of size 100 is taken resulting in a standard deviation of 3. Construct a 95% confidence interval for the population variance.
63. ### Statistics

A confidence interval for a population mean has a margin of error of 3.1. a)Determine the length of the confidence interval. b)If the sample mean is 56.7, obtain the confidence interval.
64. ### stats

A financial institution wishes to estimate the mean balances owed by its credit card customers. The population standard deviation is estimated to be \$300. If a 98 percent confidence interval is used and an interval of ±\$75 is desired, how many cardholders should be sampled? A...
65. ### Statistics

Problem 1 Use the Old Faithful data labelled Duration as a sample for problem 1. a. Determine the proportion of instances that the duration was less than 240 seconds. Also express the proportion as a percent. (hint: proportion is number of successes divided by total number. b...
66. ### Statistics

(25 pts, 5 pts each) The ounces of coffee that a machine dispenses in 5-ounce cups have normally distributed. Suppose a sample of size 6 was taken from this machine, as shown as follows: 5.05 5.03 5.10 5.02 4.98 5.00 (for all calculations, keep at least six decimal places) (1...
67. ### statistics

What do confidence intervals represent? What is the most controllable method of increasing the precision of or narrowing the confidence interval? What percentage of times will the mean, or population proportion, not be found within the confidence interval?
68. ### statistics

A large school district would like to estimate the mean score for all of its 5th grade students on a certain mathematics achievement test known to produce scores that are normally distributed in this population. In a pilot study, n = 25 randomly selected 5th graders take the ...
69. ### statistics

A researcher wants to carry out a hypothesis test involving the mean for a sample of n = 20. While the true value of the population standard deviation is unknown, the researcher is reasonably sure that the population is normally distributed. Given this information, which of ...
70. ### math

20 students, a score of 10 indicates depression, a score of 0 indicates no depression, variation is unknown, but sample of 20 has a mean score of 4.4, unbiased estimate of population variance is 15. What is the variance of the distribution of means?
71. ### Math - Pre-Algebra

44) A financial institution wishes to estimate the mean balances owed by its credit card customers. The population standard deviation is estimated to be \$300. If a 98 percent confidence interval is used and an interval of ±\$75 is desired, how many cardholders should be ...
72. ### statistics

Can someone guide me on how to solve this problem: A sample of 52 night students ages is obtained in order to estimate the mean age of night school students. sample mean = 25.9 years. the population variance is 23. Give a point estimate for the mean. Find the 95% confidence ...
73. ### stats

The following data were collected from a case-control study of breast cancer and fat intake: case control High-fat diet 10 5 Low-fat diet 40 55 50 60 Statistical inferences for odds ratios are based on the natural log of the odds ratio, rather than the odds ratio itself (...
74. ### statistics

3. A researcher is interested in whether listening to music helps or hinders test-performance. To control for differences in cognitive level, this researcher decides to use a within-participants design. He selects a random sample of participants and has them study different ...
75. ### college

The results from an independent-measures research study are being used to estimate how much difference there is between two treatments. If the study used a total of n = 10 participants, then the t values for a 90% confidence interval would be __________.
76. ### stat and research

3. A researcher is interested in whether listening to music helps or hinders test-performance. To control for differences in cognitive level, this researcher decides to use a within-participants design. He selects a random sample of participants and has them study different ...
77. ### statistics

4. Assume you are just planning this survey and want to know how many individuals you have to randomly select to be part of the sample. Assume that the purpose of the study is to calculate a 95% confidence interval for proportion of the adult population who favor lowering the ...
78. ### stats

A research firm conducted a survey to determine the mean amount people spend at a popular coffee shop during a week. They found the amounts spent per week followed a normal distribution, with a population standard deviation of \$4. A sample of 49 customers revealed that the ...
79. ### Statistics

A study of 420,048 cell phone users found that 135 of them developed cancer of the brain or nervous system. prior to this study of cell phone use the rate of such cancer was found to be 0.0333% for those not using cell phones. Complete parts (a) and (b) a. use the sample data ...
80. ### Statistics

Consider a study in which the population variance estimate based on treatment group of 14 participants is 8, and the population variance estimate based on a control group of 17 individuals is 9. Compute the pooled estimate of population variance. - 7.25 - 8.55 - 9.22 - 10.05
81. ### statistics

Consider a study in which the population variance estimate based on treatment group of 14 participants is 8, and the population variance estimate based on a control group of 17 individuals is 9. Compute the pooled estimate of population variance.
82. ### statistical applications

In the media, numerous surveys are often displayed reporting percentages or proportions. A margin of error is often reported in the survey and this is used to calculate confidence intervals. Why is it important to create/report confidence intervals (CI) rather than just ...
83. ### Math-Stat Help

In a random sample of 78 teenagers, 32 admit to texting while driving. Construct a 98% confidence interval for the percentage of teenager that text while driving. Start by showing that conditions for constructing a confidence interval are met. 1) Check conditions 2) confidence...

A random sample of size 15 taken from a normally distributed population reveled a sample mean of 75 and a sample variance of 25. The upper limit of a 95% confidence interval for the population mean would equal?
85. ### statistics

A consumer magazine has contacted a simple random sample of 33 owners of a certain model of automobile and asked each owner how many defects had to be corrected with in the first 2 months of ownership. The average number of defects was x with (with line over the x)=3.7, with a...
86. ### Probability

Let X be a continuous random variable. We know that it takes values between 0 and 3 , but we do not know its distribution or its mean and variance. We are interested in estimating the mean of X, which we denote by h . We will use as a conservative value (upper bound) for the ...
87. ### Stastics

Which of the following descriptions of confidence intervals is correct? (Select all that apply) a. If a 95% confidence interval contains 0, then the 99% confidence interval contains 0 b. If a 99% confidence interval contains 0, then the 95% confidence interval contains 0 c. If...
88. ### hypothesis testing and CI

A hypothesis test for a population mean is to be performed at the 5% level of significance. The population standard deviation is known. The hypotheses are H0: ƒÊ = 80 Ha: ƒÊ ‚ 80. A 95% confidence interval for ƒÊ is also constructed. True or false, if 80 lies within ...
89. ### statstics

construct a 90 confidence interval for the population mean ÃŽ¼. assume the population has a normal distribution. A sample if 15 randomly selected math majors has a grade point average of 2.86 with a standard deviation od 0.78. Round to the nearest hundredth
90. ### stat

Construct a 90% confidence interval for the population mean. Assume the population has a normal distribution. A same of 15 randomly selected math majors has a grade point average of 2.86 with a standard deviation of 0.78. Round to the nearest hundredth. Answers: a) (2.41,3.42...
91. ### Statistics in Psychology

QUESTION 25: In a study you obtain the following data representing the aggressive tendencies of some football players:40 30 39 40 41 39 31 28 33(a) Researchers have found that  is 30 in the population of nonfootball players, 1X 5 5. 2 Using both tails of the sampling ...
92. ### Statistics

. As the sample size increases The confidence interval also increases (gets larger) The confidence interval decreases (gets smaller) The confidence interval stays the same The population mean increases.
93. ### stat

Which of the following statements is true about the t-distribution with k degrees of freedom? i. the t-distribution is symmetric ii. the t-distribution with k degrees of freedom has a smaller variance than the t-distribution with k+1 degrees of freedom iii. the t-distribution ...
94. ### statistics

A random sample of 10 observations has been drawn from a normal population, and the sample variance is found to be s² = 19.5. Determine the 98% confidence interval for ó².
95. ### Statistics

A confidence interval was used to estimate the proportion of statistics students that are females. A random sample of 72 statistics students generated the following 90% confidence Interval: (.43, .63). based on the interval above, is the population proportion of females equal ...
96. ### Stats (Math)

Assume that Science scores on a 25-point quiz for a random sample of 5 students were drawn from a normal population. The assumed variance was 20 while the recorded variances were: 18, 16, 10, 13, and 23. You suspected that the variance is actually higher. What test do you need...
97. ### Statistics

A confidence interval was used to estimate the proportion of statistics students that are females. A random sample of 72 statistics students generated the following 90% confidence interval: (0.438, 0.642). Based on the interval above, is the population proportion of females ...
98. ### statistics

Suppose X has a mound-shaped distribution with sigma=9. A random sample of size 36 has a sample mean 20. Is it appropriate to use a normal distribution to compute a confidence interval for the population mean u?
99. ### Math Stats

A random sample of 30 plants has a sample standard deviation of 3.4 days for maturity. A 95% confidence interval for the population variance is __ to __days.
100. ### statistics

1. Prospective Cohort Study The following tables show the crude and sex-specific results from a Prospective Cohort Study that examines the association between a binary exposure (E) and the development of a disease (D) during 20 years of follow-up. Full Data: Sex-Specific Data...