Wednesday
July 23, 2014

Posts by MathGuru


Total # Posts: 1,443

Introduction to statistics
Formula to find sample size: n = [(z-value)^2 * p * q]/E^2 ... where n = sample size, z-value is found using a z-table for 99% confidence, p = .50 (when no value is stated in the problem), q = 1 - p, ^2 means squared, * means to multiply, and E = 0.19. Plug values into the for...

statistics
Hint: The mean of the sampling distribution is the population mean.

statistics, probability
Formula (if you don't use the binomial probability table): P(x) = (nCx)(p^x)[q^(n-x)] Values: n = 6 p = 0.4 q = 1 - p = 1 - 0.4 = 0.6 i. Find P(5) ii. Find P(4), P(5), and P(6). Add together for your total probability. iii. I'll let you try this one on your own. I hope...

statistics
standard error = s/√n Note: The square root of the variance is called the Standard Deviation With your data: 2 = (4.472)/√n Solve for n. I hope this is what you were asking.

statistics
CI95 = 51.4 ± 1.96 (16.66) Calculate to determine the interval.

Correction
Substitute t for z in my statements. Sorry for any confusion.

Statistics
Since your sample size is small, you can use a one-sample t-test formula. With your data: z = (2.8 - 3)/(0.3/√10) Finish the calculation. Next, check a t-table using 9 degrees of freedom (which is n - 1) for a one-tailed test at .05 level of significance. Compare your z-...

statistics
Here's one way you might do this: s/[1 + (2.58/√2n)] to s/[1 - (2.58/√2n)] Note: 2.58 represents 99% confidence Find the standard deviation for your data. Use that value for s. Your sample size is 12. I'll let you take it from here.

statistics
Here's one way to do this problem: n = 240 p = .03 q = 1 - p = 1 - .03 = .97 For (a), you will need to find P(0) through P(4). Add together, then subtract the total from 1 for the probability. I'll let you try (b). You can use a binomial probability table or calculate ...

stats
I'll help with the last two: 9. The alternate hypothesis shows a specific direction in a one-tailed test. 10. 2.262 (degrees of freedom would be n - 1)

Statistics (Check Work)
Looks like you have a good handle on this, Jen. Keep up the good work!

Statistics (Check Work)
I see you figured this out on your own. Good job!

Statistics (Check Work)
Hi Jen! Just an FYI: I'm a "she" instead of a "he" but thanks for the compliments. I'm always glad to help when and where I can. Let's get started. Both questions are the same type of problem. Question 1: Null: pR = pU Alternate: pR > pU Form...

Statistics
PsyDAG answered a similar post. See below under "Related Questions" for the prior posting.

statistics
You might try a formula like this one: s/(1 + 1.96/√2n) to s/(1 - 1.96/√2n) Substitute and calculate. There may be other variations of similar formulas you can use as well.

statistics
Try z-scores. In this case, use the following: z = (x - mean)/(sd/√n) With your data: z = (165 - 150)/(90/√25) I'll let you finish the calculation. Next, check a z-table for the probability. Remember the question says "165 friends or more" when you ar...

statistics
95% confidence interval is equivalent to z = 1.96, so if you round to 2, then your calculations for E are almost correct. I think you missed a 0; I get E = 0.04248. The formula used to determine the margin of error is all you should need to answer the problem.

Statistics
Try the binomial probability formula: P(x) = (nCx)(p^x)[q^(n-x)] n = 15 x = 4 p = .20 q = 1 - p = .80 Substitute the values into the formula and calculate your probability.

Statistics (Check Answer)
You are welcome! I'm glad the explanation helped.

Statistics (Check Answer)
Some notes on finite population correction factor: If the population is small and the sample is large (more than 5% of the small population), use the finite population correction factor. For standard error of the mean, use: sd/√n If you need to adjust for the finite pop...

Statistics
Formula: n = {[(z-value) * sd]/E}^2 ...where n = sample size, sd = standard deviation, E = maximum error, and ^2 means squared. Using the values you have in your problem: n = {[(1.96) * 15]/3}^2 Calculate for sample size. Round your answer.

statistics
Formula: n = {[(z-value) * sd]/E}^2 ...where n = sample size, sd = standard deviation, E = maximum error, and ^2 means squared. Using the values you have in your problem: n = {[(1.96) * 15]/3}^2 Calculate for sample size. Round your answer.

statistics
Let's try a binomial proportion one-sample z-test. Ho: p = 0.65 Ha: p does not equal 0.65 Test statistic: z = (0.49 - 0.65)/√[(0.65)(0.35)/100] z = -3.35 The null would be rejected at the .05 level for a two-tailed test (p does not equal 0.65). Use a z-table to find ...

Statistics
Standard deviation = √npq 1) n = 157 p = .16 (for 16%) q = 1 - p = 1 - .16 = .84 2) n = 209 p = .12 (for 12%) q = 1 - p = 1 - .12 = .88 Substitute and calculate.

Statistics
The closer it is to 1 or -1, the stronger the correlation. A correlation of 0.3 is a weaker relationship between variables.

Statistics
Try z-scores: z = (x - mean)/sd Your data: 2.33 = (x - 40)/1 Solve for x. Note: 2.33 represents the z-score corresponding to the 1% in your problem.

Stats
Formula: P(x) = (nCx)(p^x)[q^(n-x)] Your data: x = 2 p = .05 q = 1 - p = 1 - .05 = .95 n = 20 Substitute and calculate for your probability.

Stats
Formula to find sample size: n = [(z-value)^2 * p * q]/E^2 ... where n = sample size, z-value is 1.96 and is found using a z-table for 95% confidence, p = .5 (when no value is stated), q = 1 - p, ^2 means squared, * means to multiply, and E = .02 (or 2%). I'll let you take...

STATISTICS
Formula: P(x) = (nCx)(p^x)[q^(n-x)] For (a): x = 5 p = .16 q = 1 - p = 1 - .16 = .84 n = 29 Substitute and calculate for your probability. For (b): x = 0,1,2,3,4 p,q,n stay the same. Add each probability you calculate for the total probability. For (c): Add together the probab...

Stat
You will need a confidence interval formula for the difference of two population means. Use 1.96 for z (representing 95% confidence). Substitute what you know into the formula and calculate.

statistics
Using a Poisson distribution: P(x) = (e^-μ) (μ^x) / x! e = 2.71828 µ = 1.4 x = 4 Substitute and calculate.

Statistics
Use a one-sample z-test for proportions. With your data: z = (.43 - .50)/√(.50)(.50)/1000) = -4.358 Reject the null and accept the alternate hypothesis (p < .50).

Correction
Correction: Your calculation is correct. z = 5.156 You would still reject the null and accept the alternate hypothesis. Sorry for any confusion.

Statistics
Formula: z = (sample mean - population mean)/(standard deviation divided by the square root of the sample size) With your data: z = (26600 - 25000)/(3800/√150) = 4.96 You can reject the null and accept the alternate hypothesis (µ > 25000).

statistics
Hypotheses: Ho: µ = 10 -->null hypothesis Ha: µ < 10 -->alternate hypothesis

Statistics
z = 2.575 for a 99% confidence. Since your sample sizes are large, I would use a two-sample confidence interval formula for large sample sizes. Critical value at .05 using a z-table for a one-tailed test is z = 1.645 If you use a t-table instead to find critical value, then yo...

Biology
Here are a few of your questions; maybe you can determine the rest. 14. dermis 15. chemical 16. urine 17. viruses 18. antibodies I'll let you take it from here.

Statistics
Using this formula: P(x) = (nCx)(p^x)[q^(n-x)] Note: q = 1 - p We have: P(x) = (3Cx)(.52^x)[.48^(3-x)]

biology
(B) T cells

Stats
Use z-scores. For this problem: z = (x - mean)/(sd/√n) With your data: z = (8.2 - 8)/(2/√100) = 1.00 z = (8.8 - 8)/(2/√100) = 4.00 Answer: .1586 is the probability (check a z-table between z = 1.00 and z = 4.00)

Statistics
a) ± 3.1 b) 56.7 - 3.1 = 53.6 56.7 + 3.1 = 59.8 Interval is 53.6 to 59.8

please help Human bio
A. elastin B. collagen C. telomeres Check this!

ap stats
50th percentile

statistics
Welch's t-test for unequal variances: t = (mean1 - mean2)/√(s^2/n1 + s^2/n2) t = (4.31 - 3.68)/√(0.17^2/10 + 0.22^2/10) t = 0.63/0.08792 = 7.166 (rounded)

Statistics
If you do a proportional z-test with this data, it would look something like this: z = (.258 - .20)/√[(.20)(.80)/120] Note: 31/120 = .258 Calculating: z = .058/.0365 = 1.589 The null would not be rejected and the conclusion would be that there is no difference in the pop...

Statistics
Answer: That Y increases by 20 units for each unit increase in X.

Stat college
Mean = np = 9 * .17 = 1.53 Use binomial probability formula (or a binomial probability table). Formula: P(x) = (nCx)(p^x)[q^(n-x)] x = 0,1,2 n = 9 p = .17 q = 1 - p = 1 - .17 = .83 For first part: Find P(2) for probability. For second part: Find P(0) and P(1). Add P(0), P(1), ...

STAT
Mean = np = 9 * .17 = 1.53 Use binomial probability formula (or a binomial probability table). Formula: P(x) = (nCx)(p^x)[q^(n-x)] x = 0,1,2 n = 9 p = .17 q = 1 - p = 1 - .17 = .83 For first part: Find P(2) for probability. For second part: Find P(0) and P(1). Add P(0), P(1), ...

Statistics (45)
Formula: n = {[(z-value)(sd)]/E}^2 a) n = [(1.96 * 7)/2]^2 b) n = [(2.575 * 7)/2)^2 Calculate. Round to the next highest whole number.

Statistics (44)
Formula: n = {[(z-value)(sd)]/E}^2 a) n = [(1.96 * 6.35)/2]^2 b) n = [(1.96 * 6.35)/1)^2 Calculate. Round to the next highest whole number.

Statistics (43)
Find mean and standard deviation, then use confidence interval formula. CI95 = mean ± 1.96(sd/√n) n = 20 I'll let you take it from here.

Statistics (42)
I'll get you started. a) CI95 = mean ± 1.96 (sd/√n) mean = 96 sd = 16 n = 60 b) Use the same formula, except n = 120 c) Compare the margin of error in a) and b) to answer this question.

Statistics (39)
Some notes on finite population correction factor: If the population is small and the sample is large (more than 5% of the small population), use the finite population correction factor. For standard error of the mean, use: sd/√n If you need to adjust for the finite pop...

Statistics (38)
Mean is 4550.7 (add up the numbers and divide by 10) I'll let you determine standard deviation. Use a calculator, or if you do it by hand, use a formula to calculate the standard deviation.

Statistics
How about a one-sample t-test? Your sample size is fairly small. Fill in what you know into the formula to calculate the test statistic. population mean = 100 sample mean = 115 standard deviation = 30 sample size = 22 I'll let you take it from here.

Statistics
CI98 = p ± 2.33 √(pq/n) p = 42/200 = .21 q = 1 - p = 1 - .21 = .79 n = 200 With your data: CI98 = .21 + 2.33 √[(.21)(.79)/200] I'll let you take it from here to finish.

statistics
Formula: n = [(z-value)(p)(q)]/E^2 z-value = 2.33 for 98% confidence p = .5 if no value is stated q = 1 - p E = Maximum error With your data: n = [(2.33)(.5)(.5)]/.03^2 I'll let you take it from here. Round to the next whole number.

statistics
Formula: P(x) = (nCx)(p^x)[q^(n-x)] Find P(0), then subtract that value from 1. n = 12 p = .25 q = 1 - p I'll let you take it from here.

statistics
How about d?

statistics
How about d? You have only one sample with a small sample size.

statistics
How about d?

statistics
Using an online calculator: Standard Deviation = 9.21 To find variance, square the standard deviation.

Statistics
I think you are correct!

Statistics
See later post.

Statistics
D. All of the above.

Statistics
D. Either (b) or (c).

Statistics
C. µ1 and µ2 to be unequal.

ap statistics
CI95 = p ± 1.96[√(pq/n)] p = 20/75 = .27 q = 1 - p = 1 - .27 = .73 n = 75 Substitute into the formula to find the confidence interval.

statistics
Try a one-sample t-test since your sample size is small. You will need to calculate the mean and standard deviation. Use a t-table to find the critical value at .05 level of significance for a one-tailed test. Degrees of freedom is (n - 1). Sample size (n) is 9.

Statistics
2.46 A Type I error is rejecting the null when it is true. If the critical value is 2.45, and you have a test statistic of 2.46, you have the least chance among the other choices of rejecting the null and it happens to be true.

statistics
If you have equal sample sizes and unequal standard deviations, a Welch's t-test might be appropriate. Check degrees of freedom for this type of test before checking the appropriate table to determine critical value.

statistics
True.

Statistics
Second choice. Do not reject the null hypothesis because 1.457 lies in the region between -2.326 and 2.326.

statistics
Both A and B.

ap statistics
Since the probability of a Type II error is equal to beta, I would say D is not correct.

ap statistics
B. The probability of rejecting H0 when HA is true.

ap statistics
The population mean is equal to the mean of the sampling distribution of the sample means. Standard error of the mean is the standard deviation of the sample means.

Statistics
I would think either one due to the nature of the tests, but check this to be sure.

statistics
Try this formula: n = [(z-value)^2 * p * (1-p)]/E^2 ...where n = sample size you need, z-value = 1.96 to represent 95% confidence, p and 1-p represent proportions, E = .025 (or 2.5%), and ^ means squared. With your data: n = [(1.96)^2 * .30 * .70]/.025^2 I'll let you finis...

statistics
Try this formula: n = [(z-value * sd)/E]^2 With your data: n = [(1.96 * 40)/10]^2 I'll let you finish the calculation. Remember to round the answer to the nearest whole number.

statistics
Part a) ME = 1.96 * sd/√n With your data: ME = 1.96 * 65/√45 Part b) CI95 = mean ± 1.96(sd/n) With your data: CI95 = 273 ± 1.96(65/√45) I'll let you finish the calculations.

statistics
Use a t-table to determine the area. Remember to use the degrees of freedom when looking at the table.

statistics
Part a) SE of mean = sd/√n = 5/√40 Part b) ME = 1.96 * 5/√40 I'll let you finish the calculations.

Stats
0.1359 is the area under the normal curve between z = -1 and z = -2 Look at a normal distribution table (z-table) to check.

Statistics
Type I errors result when you reject the null and it's true. Type II errors result when you accept the null and it's false. If you reject the null hypothesis that the subject is guessing and it's true, you have made a Type I error. If you accept the null that the ...

statistics
Standard error of the proportion is: √(pq/n) p = .55 q = 1-p = .45 n = sample size I'll let you take it from here.

statistics
Some notes on finite population correction factor: If the population is small and the sample is large (more than 5% of the small population), use the finite population correction factor. For standard error of the mean, use: sd/√n If you need to adjust for the finite pop...

personal finance
Common stock

Statistics
1. Relationship condition (the two variables must be related) 2. Temporal condition (time order) 3. Lack of other explanation condition (not due to confounding variables, etc.)

statistics
Regression equation: predicted y = a + bx ...where a represents the y-intercept and b the slope. In your equation, b (slope) = 0.0712

Science
If the current is held constant, an increase in voltage will result in an increase in resistance.

Statsistics
Here is a hint: It doesn't matter if the correlation is negative or positive, the closer it is to zero, the weaker the correlation.

stats
Use a confidence interval formula for the data. Here is an example of one for a 95% confidence interval: CI95 = mean ± 1.96 (sd/√n)

statistics
Use a one-sample z-test. Calculate to find the test statistic. Find the critical value using a z-table for .05 significance level for a one-tailed test. The p-value is the actual level of the test statistic and is found using a z-table as well.

science
Velocity = Frequency * Wavelength V = 5 hertz * 10 mm V = ? I'll let you finish.

Statistics PLEASE HELP ME!
You might try this formula: Pr[T ≤ t] = 1 - e^-ht h = reciprocal of the mean t = time Therefore, the reciprocal of 25 is 1/25 or .04 Substituting into the formula: Pr[T ≤ 20] = 1 - e^-.04(20) = 1 - e^-.8 = 1 - .4493 = .5507 Check these calculations.

Statistics
Use confidence interval formulas for proportions. CI95 = p + or - (1.96)(√pq/n) ...where √ = square root, p = x/n, q = 1 - p, and n = sample size. CI90 = p + or - (1.645)(√pq/n) Hint: x = 396, n = 621 Convert all fractions to decimals to work the formulas. I ...

Statistics
Use confidence interval formulas for proportions. CI95 = p + or - (1.96)(√pq/n) ...where √ = square root, p = x/n, q = 1 - p, and n = sample size. Hint: x = 150, n = 240 Convert all fractions to decimals to work the formulas. I hope this will help get you started.

Statistics
I think you are referring to "dummy coding" but you may want to check this.

statistics
You can try a proportional one-sample z-test for this problem. Check a table for the critical value to compare to the test statistic. If the test statistic exceeds the critical value, then reject the null and accept the alternative hypothesis.

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