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.

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.

... As size of the mean difference increases, Cohen's d increases. ... Explain how the power of a hypothesis test is influenced by each of the following. ...

... As size of the mean difference increases, Cohen's d increases. ... Explain how the power of a hypothesis test is influenced by each of the following. ...

... c. Compute Cohen's d measure effect size for both ...d. Briefly describe how sample size influence the ...hypothesis testing, statistical decisions, power, Type I ...

... error and the test statistic for every hypothesis test? ... the effect-size statistic, such as Cohen's d, neutralizes the ... How does power relate to Type II errors? ...

... 2 2t For independent sample test Cohen's d = = -0.78116 d. f. 5. Estimate the Power for 2 and 3 above. Your text provides the appropriate tables. Find them!! ...

... than for an independent groups design (see Cohen, 1988, and ... per- taining to the calculation of d in these ... NHST, and also a measure of power, especially when a ...

... desire to measure a large effect (Cohen's d ≥ 0.8), then ... enter 0.80 as your desired power Group sizes ... equal, and assume the alternative hypothesis that they ...

... The solution gives detailed steps on explaining 6 basic statistics questions including hypothesis testing, power of test, cohen's d coefficient and so on. ...

... larger than .05, we fail to reject the null hypothesis. ... is in the moderately large range for Cohen's d. Since our ... when we look at the concept of power, we'll ...