Descriptive Statistics and Mean-Level Comparisons Assignment

Descriptive Statistics and Mean-Level Comparisons Assignment

Barker and colleagues (2012) compared 61 parents fo children who had a serious mental illness (SMI) to 321 parents of children withour such an illness. The researchers examined the parents’ reported levels of stress, their levels of a hormone called cortisol (levels of this hormone provide an indication of chronic stress), and their use of several types of medication. The table below shows the results of the study. Focusing on the parents’ number of stressors (the first row of the table) and the parents’ use of medications for anxiety or depression (the last row in the table), explain these results to a person who knows about the t test for a single sample but is unfamiliar with the t test for independent means.
Descriptive Statistics and Mean-Level Comparisons
SMI Parents Comparison Parents
N = 61 N = 321
Mean SD Mean SD t p
Stress
Number of stressors 0.65 0.56 0.42 0.37 -3.08 0.00
Stress severity sum 1.89 1.63 1.16 1.1 -3.3 0.00
Cortisol (nmol/L)
Wake 17.46 10.72 16.75 7.38 -0.14 0.90
Out of bed 22.83 11.48 24.19 10.59 1.13 0.26
Bed 5.72 8.56 4.22 5.57 -1.86 0.06
Cortisol awakening response 5.62 9.7 7.48 8.34 1.55 0.12
Decline from out of bed 17.13 11.35 20.11 10.71 1.97 0.05
Medication use (proportion)
Allergy 0.26 0.44 0.16 0.37 -1.71 0.09
Steroid 0.2 0.4 0.12 0.33 -1.32 0.19
Hormone 0.13 0.34 0.14 0.35 0.25 0.80
Anxiety or depression 0.26 0.44 0.12 0.33 -2.36 0.02

14. For each of the following studies, say whether you would use a t test for dependent means or a t test for independent means.

a. A researcher measures the heights of 40 university students who are the firstborn in their families and compares the 15 who come from large families to the 25 who come from smaller families.

b. A researcher tests performance on a math skills test of each of 250 individuals before and after they complete a one-day seminar on managing test anxiety.

c. A researcher compares the resting heart rate of 15 individuals who have been taking a particular drug to the resting heart rate of 48 other individuals who have not been taking the drug.