Self-efficacy is a general concept that measures how well we think we can contro
ID: 3177288 • Letter: S
Question
Self-efficacy is a general concept that measures how well we think we can control different situations. A multimedia program designed to improve dietary behavior among low-income women was evaluated by comparing women who were randomly assigned to intervention and control groups. Participants were asked, "How sure are you that you can eat foods low in fat over the next month?" The response was measured on a five-point scale with 1 corresponding to "not sure at all" and 5 corresponding to "very sure." Here is a summary of the self-efficacy scores obtained about 2 months after the intervention:
x
(a) Do you think that these data are Normally distributed? Choose one
-The distribution is not Normal because all scores are integers.
-The distribution is not Normal because the sample included only women.
- The distribution is Normal because the sample sizes are large.
-The distribution is Normal because the sample was randomly assigned.
-The distribution is Normal because the standard deviation is smaller than the mean.
(b) Is it appropriate to use the two-sample t procedures that we studied in this section to analyze these data? Choose one
-The t procedures should not be appropriate because the sample sizes are not large enough.
-The t procedures should be appropriate because we have two large samples with no outliers.
-The t procedures should be appropriate because we have Normally distributed data.
-The t procedures should not be appropriate because we do not have Normally distributed data.
-The t procedures should not be appropriate because the two groups are different sizes.
(c) Describe appropriate null and alternative hypotheses. Choose on
-H0: Intervention = 2; Ha: Intervention > Control (or Intervention = Control)
-H0: Intervention 2; Ha: Intervention > Control (or Intervention = Control)
-H0: Intervention = 2; Ha: Intervention < Control (or Intervention Control)
-H0: Intervention = 2; Ha: Intervention > Control (or Intervention < Control)
-H0: Intervention 2; Ha: Intervention < Control (or Intervention = Control)
Some people would prefer a two-sided alternative in this situation while others would use a one-sided significance test. Choose the correct reason.
-The one-sided alternative reflects the researchers' (presumed) belief that the intervention would decrease scores on the test. The two-sided alternative allows for the possibility that the intervention might have had a positive effect.
-The two-sided alternative reflects the researchers' (presumed) belief that the intervention would increase scores on the test. The one-sided alternative allows for the possibility that the intervention might have had a negative effect.
-The one-sided alternative reflects the researchers' (presumed) belief that the intervention would increase scores on the test. The two-sided alternative allows for the possibility that the intervention might have had a negative effect.
-The two-sided alternative reflects the researchers' (presumed) belief that the intervention would decrease scores on the test. The one-sided alternative allows for the possibility that the intervention might have had a positive effect.
-The one-sided alternative reflects the researchers' (presumed) belief that the intervention would decrease scores on the test. The two-sided alternative allows for the possibility that the intervention might have had a negative effect.
(d) Carry out the significance test using a one-sided alternative. Report the test statistic with the degrees of freedom and the P-value. (Round your test statistic to three decimal places, your degrees of freedom to the nearest whole number, and your P-value to four decimal places.)
Write a short summary of your conclusion. Choose the correct one below.
-We reject H0 and conclude that the intervention increased test scores.
-We do not reject H0 and conclude that the intervention had no significant effect on test scores.
(e) Find a 95% confidence interval for the difference between the two means. Compare the information given by the interval with the information given by the significance test.
(f) The women in this study were all residents of Durham, North Carolina. To what extent do you think the results can be generalized to other populations? Choose one
-The results for this sample will generalize well to all other areas of the country.
-The results for this sample may not generalize well to other areas of the country.
Group nx
s Intervention 166 4.15 1.19 Control 213 3.61 1.12Explanation / Answer
a) Correct Answer: Option (C)
The distribution is Normal because the sample sizes are large.
b) Correct Aswer: option (c )
The t procedures should be appropriate because we have Normally distributed data.
(c) Correct Answer: Option (a)
H0: Intervention = 2; Ha: Intervention > Control (or Intervention = Control)
(d)
Eq. vars: Pool
Test Statistic, t: 4.5309
Critical t: ±1.966274
P-Value: 0.0000
Degrees of freedom: 377.0000
Here P-value < alpha 0.05, so we reject H0
Thus, we conclude that Intervention = 2
e)
95% Confidence interval:
0.305655 < µ1-µ2 < 0.774345
f) Correct Answer: The results for this sample will generalize well to all other areas of the country.
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