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April 19, 2014

April 19, 2014

**Recent Homework Questions About Statistics**

Post a New Question | Current Questions

**Statistics**

The weights of male babies less than 2 months old in the United States is normally distributed with a mean of 11.5 pounds and a standard deviation of 2.7 pounds. Find the 80th percentile score for these weights. I don't have a table, I have to figure it out using the TI-84...
*Tuesday, February 25, 2014 at 7:13pm*

**Statistics**

The law of large numbers tells us what happens in the long run. Like many games of chance, the numbers racket has outcomes so variable - one three-digit number wins $600 and all others win nothing - that gamblers never reach "the long run." Even after many bets, ...
*Tuesday, February 25, 2014 at 7:10pm*

**Statistics**

Substitute 16 for x and solve for tread depth in the equation.
*Tuesday, February 25, 2014 at 7:09pm*

**Statistics 101**

Probably the better answer would be "wider" than 90% confidence interval.
*Tuesday, February 25, 2014 at 7:02pm*

**Statistics**

Try z-scores: z = (x - mean)/sd Substitute the data into the above formula and solve for x. mean = 11.5 sd = 2.7 z = score from the table Use the table to find z-score at the 80th percentile. I'll let you take it from here.
*Tuesday, February 25, 2014 at 6:59pm*

**Statistics**

.0051
*Tuesday, February 25, 2014 at 6:59pm*

**Statistics 101**

...greater than 90% confidence interval.
*Tuesday, February 25, 2014 at 6:56pm*

**statistics**

I'll get you started. Hypotheses: Ho: µ = 12 --> this is the null hypothesis Ha: µ ≠ 12 ---> this is the alternate or alternative hypothesis Note: Null hypothesis always uses an equals sign. The alternate or alternative hypothesis in this case uses ...
*Tuesday, February 25, 2014 at 6:48pm*

**Statistics 101**

A researcher plans to use a random sample of n= 500 families to estimate teh mean monthly family incomefor a large population. a 99% confidence interval based on the sample would be _________ than 90% confidence interval.
*Tuesday, February 25, 2014 at 6:43pm*

**Statistics**

The weights of male babies less than 2 months old in the United States is normally distributed with a mean of 11.5 pounds and a standard deviation of 2.7 pounds. Find the 80th percentile score for these weights.
*Tuesday, February 25, 2014 at 6:18pm*

**Statistics**

The law of large numbers tells us what happens in the long run. Like many games of chance, the numbers racket has outcomes so variable - one three-digit number wins $600 and all others win nothing - that gamblers never reach "the long run." Even after many bets, ...
*Tuesday, February 25, 2014 at 5:39pm*

**Statistics**

(29-25)/4= 4/4= 1
*Tuesday, February 25, 2014 at 5:35pm*

**statistics**

Suppose a manufacturer claims that each family-size bag of pretzels sold weighs 12 ounces on average with a standard deviation of 0.8 ounces. A consumer's group decides to test this claim. If a simple random sample of 49 bags of pretzels gives a sample mean of 11.8 ounces...
*Tuesday, February 25, 2014 at 5:31pm*

**Statistics**

It is 99%, sorry for the typo.
*Tuesday, February 25, 2014 at 4:30pm*

**Statistics**

The law of large numbers tells us what happens in the long run. Like many games of chance, the numbers racket has outcomes so variable - one three-digit number wins $600 and all others win nothing - that gamblers never reach "the long run." Even after many bets, ...
*Tuesday, February 25, 2014 at 3:13pm*

**Statistics**

Suppose x has a distribution with μ = 11 and σ = 5. (a) If a random sample of size n = 45 is drawn, find μx, σ x and P(11 ≤ x ≤ 13). (Round σx to two decimal places and the probability to four decimal places.)
*Tuesday, February 25, 2014 at 1:31pm*

**Statistics**

95% = mean ± 2.575 SEm SEm = SD/√n I'll let you do the calculations.
*Tuesday, February 25, 2014 at 1:30pm*

**Statistics**

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 x = 118 minutes. Suppose that we know that the study time follows a Normal distribution with...
*Tuesday, February 25, 2014 at 11:11am*

**Statistics **

In a study, nine tires of a particular brand were driven on a track under identical conditions. Each tire was driven a particular controlled distance (measured in thousands of miles), and afterward the tread depth was measured. Tread depth is measured in “mils.” Here...
*Tuesday, February 25, 2014 at 7:23am*

**statistics**

Determining whether an individual's political affliation affects his or her overall satisfaction with the economy. For this assignment, use only subjects that declared themselves as Republicans or Democrats and leave out any subjects who declared themselves as Independent ...
*Tuesday, February 25, 2014 at 12:47am*

**statistics**

A psychic was tested for ESP. The psychic was presented with 400 cards face down and was asked to determine if the card was one of four symbols: a cross, a star, a circle, or a square. The psychic was correct in 120 of the cases. Let p represent the probability that the ...
*Monday, February 24, 2014 at 7:25pm*

**statistics**

An SRS of 40 San Diego County Schools graduates showed that 26 of the 40 enrolled in a college or university right out of high school. a. Find a 90% confidence interval for the proportion of all San Diego County Schools graduates who enrolled in a college or university right ...
*Monday, February 24, 2014 at 6:19pm*

**Statistics**

Either-or probabilities are found by adding the individual probabilities. Since three face cards are already spades, delete them for the face card probability. 9/52 + 13/52 = ?
*Monday, February 24, 2014 at 1:26pm*

**statistics**

Please only post your questions once. Repeating posts will not get a quicker response. In addition, it wastes our time looking over reposts that have already been answered in another post. Thank you. See your later post.
*Monday, February 24, 2014 at 1:14pm*

**statistics**

95% = mean ± 2 SD Find the mean first = sum of scores/number of scores Subtract each of the scores from the mean and square each difference. Find the sum of these squares. Divide that by the number of scores to get variance. Standard deviation = square root of variance ...
*Monday, February 24, 2014 at 1:13pm*

**Statistics (?)**

What blanks? Z = (score-mean)/SD T = 50 + 10Z
*Monday, February 24, 2014 at 1:11pm*

**Statistics**

Fill in the blanks with the appropriate raw score, z score, t scores . Mean =50, sd = 5. Raw 35
*Sunday, February 23, 2014 at 10:16pm*

**statistics **

Construct a 95% confidence interval for the population mean. 5. Airfare A random sample of airfare prices (in dollars) for a one-way ticket airfare between two cities MN. Key: 21|1=211 21 | 1 2 22 | 1 1 1 2 3 5 7 8 23 | 2 3 4 7 7 8 9 9 24 | 2 3 4 8 8 25 | 1 2 6 6 6 6 8 9
*Sunday, February 23, 2014 at 9:37pm*

**statistics**

Construct a 95% confidence interval for the population mean. 5. Airfare A random sample of airfare prices (in dollars) for a one-way ticket airfare between two cities MN. Key: 21|1=211 21 | 1 2 22 | 1 1 1 2 3 5 7 8 23 | 2 3 4 7 7 8 9 9 24 | 2 3 4 8 8 25 | 1 2 6 6 6 6 8 9
*Sunday, February 23, 2014 at 9:29pm*

**math statistics/probability**

rfwd
*Sunday, February 23, 2014 at 9:19pm*

**Statistics**

Summarize the steps involved in analyzing the results of a one-sample experiment.
*Sunday, February 23, 2014 at 2:29am*

**Statistics**

If you pick a card at random from a well shuffled deck what is the probability you will pick a face card or a spade?
*Saturday, February 22, 2014 at 4:08pm*

**statistics**

Z = (mean1 - mean2)/standard error (SE) of difference between means SEdiff = √(SEmean1^2 + SEmean2^2) SEm = SD/√n If only one SD is provided, you can use just that to determine SEdiff. Find table in the back of your statistics text labeled something like "...
*Saturday, February 22, 2014 at 12:47pm*

**Statistics**

Please read and follow directions.
*Saturday, February 22, 2014 at 12:33pm*

**statistics**

a packaging device is set to fill detergent powder packets with a mean weight of 5kg.The standard deviation is known to be .01kg.these are known to drift upwards over a period of time due to machine fault which is not tolerable. A random sample of 100 packets is taken and ...
*Saturday, February 22, 2014 at 9:48am*

**Statistics**

Please read and follow directions.
*Friday, February 21, 2014 at 10:06pm*

**statistics**

Use a table of t-values to estimate the P-value for the specified one-mean t-test. Left-tailed test, n=12, t= -3.412. a=p<0.005. b= p>0.005. c= 0.005<p<0.01.
*Friday, February 21, 2014 at 8:09pm*

**statistics**

µ = 30 Variance for distribution of means = (SD/√n)^2 = ?
*Friday, February 21, 2014 at 4:38pm*

**Statistics**

Most problems of the "at least" type are best done by subtracting from total. P(at least one x) = 1 - P(no x's) = 1 - (25/26)^3 = 0.111 (3dp) So, Yes, you are correct.
*Friday, February 21, 2014 at 12:14pm*

**Statistics**

Selecting a letter of the alphabet: If 3 letters of the alphabet are selected at random, find the probability of getting at least one letter "x". Letters can be used more than once. My answer was: P(at least 1 "x) = 1 - (25/26)^3 = 1951/17576 or 0.11 Is this ...
*Friday, February 21, 2014 at 11:56am*

**statistics**

a. Ok b. 10/23 C. 12/77
*Friday, February 21, 2014 at 12:28am*

**statistics**

Simple question I may be over thinking 30. Gift Baskets: The Gift Basket Sore had the following premade gift baskets containing the following combinations in stock. cookies mugs candy -------------------------------------- coffee 20 13 10 tea 12 10 12 Choose 1 basket at random...
*Thursday, February 20, 2014 at 11:55pm*

**statistics**

A population is normally distributed with mean 30, population SD =10, Sample size 25. What are the mean and variance of the distribution of means, respectively?
*Thursday, February 20, 2014 at 10:35pm*

**Statistics**

Astronomers treat the number of stars in a given volume of space as a Poisson random variable. The density in the Milky Way Galaxy in the vicinity of our solar system is one star per 16 cubic light years. (a) What is the probability of three or more stars in 16 cubic light ...
*Thursday, February 20, 2014 at 8:16pm*

**Statistics**

An electronic product contains 32 integrated circuits. The probability that any integrated circuit is defective is 0.02, and the integrated circuits are independent. The product operates only if there are no defective integrated circuits. What is the probability that the ...
*Thursday, February 20, 2014 at 7:41pm*

**Statistics**

See previous post.
*Thursday, February 20, 2014 at 1:34pm*

**Statistics**

If you are comparing two means, you need to have the SEm, which requires knowledge of n. You do not supply that value. Z = (mean1 - mean2)/standard error (SE) of difference between means SEdiff = √(SEmean1^2 + SEmean2^2) SEm = SD/√n If only one SD is provided, you ...
*Thursday, February 20, 2014 at 1:33pm*

**Statistics**

m m
*Thursday, February 20, 2014 at 2:00am*

**Statistics**

P(A and B) = P(A) * P(B/A) = (0.81)* (0.92) = 0.745 The probability that a U.S. household selected at random has a computer and has Internet access is 0.745
*Thursday, February 20, 2014 at 1:10am*

**Statistics**

2. On a certain anxiety questionnaire, the population is known to have a mean of 12 and a standard deviation of 2.3. A higher score represents higher levels of anxiety. Participants in a new relaxation program complete the questionnaire after completing the program, and have a...
*Wednesday, February 19, 2014 at 11:22am*

**Statistics**

1. A company decides to add a new program that prepares randomly selected sales personnel to increase their number of sales per month. The mean number of sales per month for the overall population of sales people at this national company is 25 with a standard deviation of 4. ...
*Wednesday, February 19, 2014 at 11:20am*

**Statistics (?)**

More data is needed for us to provide help.
*Wednesday, February 19, 2014 at 11:03am*

**Statistics**

If the events are independent, the probability of both/all events occurring is determined by multiplying the probabilities of the individual events. .8 * (1-.6) = .32
*Wednesday, February 19, 2014 at 11:02am*

**statistics**

Suppose you have information that the average stress score of students in online activities is 13.15. Using Minitab, compute a one sample t-test to find out whether the stress scores reported by your sample are significantly different from those of the population of online ...
*Wednesday, February 19, 2014 at 9:01am*

**statistics**

0.53
*Tuesday, February 18, 2014 at 5:44pm*

**Statistics**

Disk of ploycarbonate plastic form a supplier are anaylzed for scratcha nd shock resistance. the results from 100 disks are summarized below: Shock Resistance high low Scratch high 70 9 resistance low 16 5 Let A denote the even that a disk has high shock resistance, and let B ...
*Tuesday, February 18, 2014 at 5:38pm*

**Statistics**

The probability that Jack plays guitar on a raining day is 0.6 and on a sunny day is 0.5. The probability that is rains tomorrow is 0.8. Find the probability that Jack will not play guitar tomorrow? Is it 32%?
*Tuesday, February 18, 2014 at 5:19pm*

**Statistics**

Hats in a box problem
*Tuesday, February 18, 2014 at 4:37pm*

**statistics**

Z = (score-mean)/SD Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score. If the events are independent, the probability of both/all events occurring is ...
*Tuesday, February 18, 2014 at 12:15pm*

**statistics**

Expect the µ's to stay the same. The standard error of the mean (SEm) = SD/√n SEm would tend to get smaller as n increases.
*Tuesday, February 18, 2014 at 12:12pm*

**statistics**

What is your Question?
*Tuesday, February 18, 2014 at 10:34am*

**statistics**

Suppose you have information that the average stress score of students in online universities is 13.15. The scores are 16, 20, 15, 12, and 14
*Tuesday, February 18, 2014 at 10:24am*

**statistics**

The personnel office at a large electronics firm regularly schedules job interviews and maintains records of the interviews. From the past records, they have found that the length of a first interview is normally distributed, with mean μ = 31 minutes and standard ...
*Tuesday, February 18, 2014 at 1:04am*

**statistics**

The taxi and takeoff time for commercial jets is a random variable x with a mean of 8.4 minutes and a standard deviation of 3 minutes. Assume that the distribution of taxi and takeoff times is approximately normal. You may assume that the jets are lined up on a runway so that ...
*Tuesday, February 18, 2014 at 1:01am*

**statistics**

Suppose x has a normal distribution with mean μ = 35 and standard deviation σ = 9. (a) Describe the distribution of x values for sample size n = 4. (Use 2 decimal places.) μx = σx = (b) Describe the distribution of x values for sample size n = 16. (Use 2 ...
*Tuesday, February 18, 2014 at 1:00am*

**statistics**

D
*Monday, February 17, 2014 at 11:41pm*

**statistics**

if n units are independent and the probability of each being up is 2/3 then the probability of all n being up is (2/3)^n HOWEVER I can not see your flow chart and therefore can not evaluate parallel paths if there are two ways to get from A to B and the probability of failure ...
*Monday, February 17, 2014 at 9:06pm*

**statistics**

Suppose that each unit of a system is up with probability 2/3 and down with probability 1/3. Different units are independent. For each one of the systems shown below, calculate the probability that the whole system is up (that is, that there exists a path from the left end to ...
*Monday, February 17, 2014 at 8:34pm*

**statistics**

tyyyy
*Monday, February 17, 2014 at 7:00pm*

**Psychology**

integrate statistics with "real-life" issues, such as day care, in order to interpret them.
*Monday, February 17, 2014 at 3:24pm*

**Statistics**

Sampling with replacement puts the chosen unit back in the pool, while without replacement does not. Probabilities remain the same with replacement, but both numerator and denominator are reduced by one in without replacement in subsequent choices.
*Monday, February 17, 2014 at 1:15pm*

**Statistics**

2
*Monday, February 17, 2014 at 11:34am*

**Statistics for social sciences**

i don't know
*Monday, February 17, 2014 at 6:09am*

**statistics**

0.745
*Sunday, February 16, 2014 at 11:36pm*

**Statistics!!!**

The correlation between number of friends and grade point average (GPA) for 50 adolescents is .37. Is this significant at the .05 level for a two-tailed test
*Sunday, February 16, 2014 at 6:26pm*

**statistics**

Researchers found that 30% of the larch trees in a certain geographical area had been damaged by fungi. (No fun, guy.) Consider a sample of 20 (independent) beach trees from the area. (a) What is the probability that fewer than half are damaged by fungi? (b) What is the ...
*Sunday, February 16, 2014 at 3:22pm*

**Statistics**

a) What is sampling with replacement? (b) What is sampling without replacement? c) How does sampling without replacement affect the probability of events, compared to sampling with replacement?
*Sunday, February 16, 2014 at 3:30am*

**statistics**

12 inches in one foot
*Sunday, February 16, 2014 at 1:22am*

**Statistics help**

a
*Sunday, February 16, 2014 at 12:02am*

**statistics**

Below are six data sets with 6 randomly selected scores in each data set. Your task is to determine if the scores were drawn from a population with μ = 5. Before you calculate the one-sample t test for each sample, make a guess as to whether or not you think the sample ...
*Saturday, February 15, 2014 at 12:17pm*

**Statistics**

b
*Friday, February 14, 2014 at 11:18pm*

**English Speech Paper (can some1 revise it)PLZ&TY**

all I need to do is add a conclusion but wanted to know if this sounded ok first. NONE of this is plagiarized I put everything but statistics in my own words :)
*Friday, February 14, 2014 at 5:12pm*

**statistics for managers**

We have no knowledge of your departments.
*Friday, February 14, 2014 at 4:28pm*

**Statistics**

Need to ask questions first to get more details. Was the sample random? Was it large enough? Was the spread statistically significant? Was the way the question was stated biased?
*Friday, February 14, 2014 at 4:24pm*

**Statistics**

http://drdavespsychologypage.homestead.com/Odds__Figuring.pdf
*Friday, February 14, 2014 at 4:17pm*

**Statistics**

Why are you substituting 5 for =? Z = (score-mean)/SD Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability (.025 because it is two-tailed) and its Z score. Insert Z first as ...
*Friday, February 14, 2014 at 3:45pm*

**Statistics**

In the population of typical college students, _ 5 75 on a statistics final exam _X 5 6.42 . For 25 students who studied statistics using a new technique, X 5 72.1. Using two tails of the sampling distribution and the .05 criterion: (a) What is the critical value? (b) Is this ...
*Friday, February 14, 2014 at 6:57am*

**Statistics**

1/5 * 100 = 20
*Thursday, February 13, 2014 at 5:55pm*

**Statistics**

There are 100 questions from a SAT test, and they are all multiple choice with possible answers of a,b,c,d,e for each question only one answer is correct. Find the mean number of correct answers for those who make random guesses for all 100 questions?
*Thursday, February 13, 2014 at 1:09pm*

**Statistics**

nope - same old 50-50 chance. Although, given their previous children, I ct the chances are high that they'll have another daughter. There may be something other than random chance at work here.
*Thursday, February 13, 2014 at 5:26am*

**Statistics**

The mean of a population of raw scores is 33 1_X 5 122 . Use the criterion of .05 and the upper tail of the sampling distribution to test whether a sample with X 5 36.8 1N 5 302 represents this population. (a) What is the critical value? (b) Is the sample in the region of ...
*Thursday, February 13, 2014 at 2:09am*

**Statistics**

Foofy asks a sample of students their choice in the election for class president. concludes that Poindexter will win. It turns out that Dorcas wins. What is the statistical explanation for Foofy’s erroneous prediction?
*Thursday, February 13, 2014 at 1:57am*

**Statistics**

A couple with eight daughters decides to have one more baby, because they think this time they are sure to have boy! Is this reasoning accurate?
*Thursday, February 13, 2014 at 1:55am*

**Statistics**

Height (ft) Interval after (min) 96 68 111 80 76 66 91 72 66 58 108 79 116 84 91 79 The data show the time intervals after an eruption (to the next eruption) of a certain geyser. Find the regression equation, letting the first variable be the independent (x) variable. Find the...
*Wednesday, February 12, 2014 at 10:15pm*

**Statistics**

A clinical trial tests a method designed to increase the probability of conceiving a girl. In the study 624 babies were born, and 312 of them were girls. Use the sample data to construct a 99% confidence interval estimate of the percentage of girls born. Based on the result, ...
*Wednesday, February 12, 2014 at 10:14pm*

**Statistics**

Critical Values for the Correlation Coefficient n alpha = .05 alpha = .01 4 0.95 0.99 5 0.878 0.959 6 0.811 0.917 7 0.754 0.875 8 0.707 0.834 9 0.666 0.798 10 0.632 0.765 11 0.602 0.735 12 0.576 0.708 13 0.553 0.684 14 0.532 0.661 15 0.514 0.641 16 0.497 0.623 17 0.482 0.606 ...
*Wednesday, February 12, 2014 at 10:14pm*

**Statistics**

Twelve different video games showing substance use were observed and the duration times of game play (in seconds) are listed below. The design of the study justifies the assumption that the sample can be treated as a simple random sample. Use the data to construct a 90% ...
*Wednesday, February 12, 2014 at 10:13pm*

**Statistics**

An IQ test is designed so that the mean is 100 and the standard deviation is 19 for the population of normal adults. Find the sample size necessary to estimate the mean IQ score of statistics students such that it can be said with 95% confidence that the sample mean is within ...
*Wednesday, February 12, 2014 at 10:12pm*

**statistics**

A false positive rate of 5% is considered to be a conservative estimate. Suppose that there are 20 employees in your company, which tests its workers weekly. What is the probability of no false-positives for this week’s test?
*Wednesday, February 12, 2014 at 7:58pm*

**statistics, math, college**

Z = (score-mean)/SD Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability (.02) and its Z score. Insert Z score and other data in above equation and solve.
*Wednesday, February 12, 2014 at 1:11pm*

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