18. A sample of n=16 individuals is selected from a normal population with a mean of µ=48 and a standard deviation of ±=12. After receiving a treatment, the sample mean is found to be M = 52.

a. Compare Cohen's d to evaluate the size of the treatment effect.

b. If the sample size were n = 36, what value would be obtained for Cohen's d? How does sample size influence the measure of effect size?

c. If the population standard deviation were ±= 24, what value would be obtained for Cohen's d? How does standard deviation influence the measure of effect size?

d. If the sample mean were M +56, what value would the obtained for cohen's d? How does the size of the mean difference influence the measure of effect size?

22. Explain how the power of a hypothesis test is influenced by each of the following. Assume that all other factors are held constant.

a. Increasing the alpha level from .01 to .05.
b. changing from a one tailed test to a two tailed test.

24. A researcher is evaluating the influence of a treatment using a sample selected form a normal distribution population with a mean u =8and a standard deviation of ±= 20. The researchers expects 12-point treatment effect and plans to use a two-tailed hypothesis test with ±= .05 .

a. Compute the power of the test if the researcher uses a sample of n = 16 individuals.
b. Compare the power of the test if the researcher uses a sample of n= 25 individuals.

Solution Summary

The solution provides step by step method for the calculation of Cohen's d and power of a hypothesis test. Formula for the calculation and Interpretations of the results are also included.

A two tailed hypothesistest is being uses to evaluate a treatment effect with o= .05. if the sample data produce a z- score of z= -2.24 what is the correct decision?
* reject the null hypothesis and conclude that the treatment has an effect
* fail to reject the null hypothesis and conclude that the treatment has no effect

A research would like to examine the effects of humidity on eating behavior. It is known that laboratory rats normally eat an average of µ = 21 grams of food each day. The research selects a random sample of n = 16 rats and places them in a controlled atmosphere room in which the relative humidity is maintained at 90%. The dail

In a study examining the effects of alcohol on reaction time it was found that even moderate alcohol consumption significantly slowed the response time to an emergency situation in a driving simulation. In a similar study researchers measured reaction times 30 minutes after each participant consumed 6 ounces of wine. Again they

8.22. Calculate the 95% confidence interval for the following fictional data regarding daily TV viewing habits: µ = 4.7; σ = 1.3 hours; sample of 78 people with a mean of 4.1 hours.
8.30. For each of the following d values, identify the size of the effect using Cohen's guidelines. (a) d = 0.79 (b) d = - 0.43 (c) d = 0

2. The value of the z-score in a hypothesistest is influenced by a variety of factors. Assuming that all other variables are held constant, explain how the value of z is influenced by each of the following.
a. Increasing the difference between the sample mean and the original population mean.
b. Increasing the population

2. For each of the following, indicate whether the factor influences the numerator or denominator of the z score and determine whether the effect would be to increase the value of z (further from zero) or decrease the value of z (closer to zero). In each case, assume that all other components of the z score remain constant.
a

8.4. What are the five steps to create a confidence interval for a z distribution?
8.6. What effect does increasing the sample size have on the standard error and the test statistic for every hypothesistest?
8.8. What does it mean to say the effect-size statistic, such as Cohen's d, neutralizes the influence of sample siz

How is hypothesistesting performed using t-tests?
What are the options for determining whether a hypothesistest result is significant?
What are critical regions for t-tests?
How is SPSS used to perform an independent samples t-test?
How are SPSS t-test results evaluated?
How do you find the p-value in SPSS, and

Let X ~ B(1,theta) (f(x) = (theta^x)*(1-theta)^(1-x) x = 0,1). To test H_0 : theta=0.25 vs H_a : theta < 0.25, we take a random sample of size 10 and reject the H_0 if and only if Sigma(x_i)<1 (i.e. the sum of all x sub i with i ranging from 1 to 10 is less than 1). Find the power function pi(theta), 0 < theta <= 0.25, of this t