Statistics and health care research exercise 31 study questions

¶ … groups whose results are reflected by the t ratios in Tables 2 and 3?

The pretest group and the post-test group.

Which't ratio in Table 2 represents the greatest relative or standardized difference between the pretest and 3 months outcomes? Is this t ratio statistically significant? Provide a rationale for your answer.

The't score that represents the greatest relative difference between pretest and 3 months is t = 4.14. The results of the analyses indicate that this is a statistically significant result, with p < .05.

Which't ratio listed in Table 3 represents the smallest relative difference between the pretest and 3 months? Is this t ratio statistically significant? What does this result mean?

The't value that is the smallest represents health responsibility and is t = 1.03. It is not statistically significant, as the analyses did not indicate it to be so (i.e. no * next to the value).

What are the assumptions for conducting a t-test for dependent groups in a study? Which of these assumptions do you think were met by this study?

There are four main assumptions that must be met when conducting a t-test for dependent groups.

i. Normal distribution of scores

ii. Interval or ratio levels of measurement for Dependent Variables iii. The groups examined for differences are dependent based on matching or subjects serving as their own control.

iv. The differences between the paired scores are independent

This study met the third assumption -- as participants were matched based on age, sex and diagnosis.

5. Compare the 3 months and 6 moths t ratios for the variable Exercise from Table 3. What is your conclusion about the long-term effect of the health promotion intervention on Exercise in this study?

The t-scores for the exercise variable from 3 months and 6 months are quite different -- t = -7.75* vs. t = -3.93*. Both were statistically significant, and the standard deviation reduced from 2.58 to 2.20. The large t score of -7.75 is indicative of differences in exercise level from pretest to 3 months. The t-test drops for 6 months, thus exercise is impacted in the long run, but the greatest difference occurred at 3 months. Thus, the health promotion intervention did not have a statistically significant effect on exercise over the long run.

6. What is the smallest, significant ratio listed in Table 2? Provide a rationale for your answer.

The smallest t-score in Table 2 is for cholesterol and it is t = 2.03*. It is significant as indicated by the *. Also, it is the smallest, regardless of valence.

7. Why are the larger t ratios more likely to be statistically significant?

When larger t-scores are found, they are often associated with smaller p values, which therefore indicate that there is a greater level of statistical significance. This means that the researcher has a greater likelihood of rejecting the null hypothesis and accepting the alternative hypothesis. Large't ratios also point to differences between control and experimental groups, when ratios are larger, we can have greater confidence that they are accurate and not simply due to chance (as indicated by the p values).