Reference no: EM132281883
Assignment -
Instructions (please read carefully): Please complete the analyses described below, then answer the questions that follow.
A researcher is planning a psychological intervention study, but before she proceeds she wants to characterize her participants' depression levels. She tests each participant on a depression index that has 8 items and each of the items is on a 1-8 response format scale. The data in your SPSS file indicates the participants' average depression score (their total depression score divided by the eight items on the index). The average depression scores are recorded in SPSS as the variable AVGdep_score.
Anyone who achieves an average depression score of 4.0 is deemed to have 'normal' levels of depression. Lower scores indicate less depression and higher scores indicate greater depression. The researcher randomly selected 40 participants to take part in the study. She wants to know whether his sample are representative of the normal population (i.e., do they score statistically significantly differently from 4.0)?
Directions (do this work in SPSS):
1. Assess the AVGdep_score scale for errors.
2. Assess the AVGdep_score scale for assumptions of hypothesis testing.
3. Run a single sample t-test.
Answer the following questions: Please type your answers (see instructions above).
1. In words, state the null and alternative hypothesis for this study.
2. Answer the following for the Average Depression Score Index:
a. What is the minimum possible value a person could score on this index?
b. What is the maximum possible value a person could score on this index?
c. What is the minimum score for participants in this sample?
d. What is the maximum score for participants in this sample?
e. Does it seem that any errors were made in the calculation of the average depression score scale?
Explain why or why not. A full credit answer should indicate the range of possible scores (min max) what your actual scores were (min max), and whether or not the actual scores fit within the range of possible scores.
The Average Depression Score Index is being treated as an interval scale of measurement so it meets Assumption 1 of hypothesis testing (the d.v. must be assessed using a scale measure (i.e., interval or ratio).
3. What should you conclude about Assumption 2? You must clearly indicate whether the data meet Assumption 2 or violate Assumption 2. Then, justify your answer by comparing the mean, the median, and the 5% trimmed mean in relation to the criteria for Assumption 2.
4. What should you conclude about Assumption 3? You must clearly indicate whether the data meet Assumption 3 or violate Assumption 3. Then, justify your answer by describing the sample size and what the skewness and kurtosis values indicate in relation to the criteria for Assumption 3.
5. Answer the following questions:
a. What is the population mean?
b. What is the estimated population standard deviation?
c. What is the sample mean?
d. What is the sample size?
e. What is the mean of the random sampling distribution of means?
f. What is the standard error of the random sampling distribution of means?
6. Answer the following questions:
a. What are the degrees of freedom?
b. What is the t test statistic?
c. What is the t critical value that PSPP would have compared the t test statistic to?
7. Based on your results, what should you conclude? Your answer should have two parts:
a) Clearly indicate whether you reject or fail to reject the null hypothesis.
b) State your results as you would report them in an academic journal.
8. Calculate the effect size and whether it is small, medium, or large.
9. Interpret your decision to reject or fail to reject the null hypothesis in light of the effect size and the 95% confidence interval of the mean difference. A full credit answer will indicate whether or not the population mean difference according to the null hypothesis falls within this interval, how that should be interpreted, and what (if any) type of error we risk making.