Question

Enter the hypothetical data below in SPSS to use for the assignment. The SPSS commands: 'file', 'new', 'data' will create a spreadsheet in which to enter the data below (manually).

Case      Group                   Test

1              1                              6

2              1                              7

3              1                              5             

4              1                              4

5              1                              1

6              2                              3

7              2                              5

8              2                              2

9              2                              5

10           2                                1

The groups are coded as follows: 1=experimental group, 2 control group. The participants in the experimental group were manipulated by being asked to write about an incident in which they were bullied, rejected or otherwise socially excluded. The control group was asked to write about what they did the previous day. The test required participants to rate the credibility of fake news stories on a scale of 1 to 10, with higher numbers indicating greater belief.

1. In conceptual terms, the hypothesis is that social exclusion increases belief in fake news. State the null and research hypotheses in statistical terms, and include the correct notation. [1 point]

2. Explain why the t test for independent samples is appropriate to test the hypothesis in terms of the formula for t. [1 point]

3. Compute the means, standard deviations. [1 point]

4. Compute and interpret the effect size (d) for the differences between means using the formula in the text (p. 219). [2 points]

5. Compute a t test for the significance of the difference between the means of the two groups. Find the critical value of the t statistic from the appropriate table in the text, or the p value from the spss output. Compare the obtained and critical value, or compare the p value in the spss output to the alpha value for the type 1 error rate.  Summarize the results of the t test. Also include the correct notation. Are the results of the test significant, i.e., likely to be found in the population? Why or why not? Should you reject or retain the null hypothesis? [4 points]

6. Summarize the results in terms of the conceptual hypothesis and variables. Explain why you think the results have practical meaning (or not). Refer to both t and d in your answer. [1 point]

Answer 1

The groups are coded as follows: 1=experimental group, 2 control group. The participants in the experimental group were manipulated by being asked to write about an incident in which they were bullied, rejected or otherwise socially excluded. The control group was asked to write about what they did the previous day. The test required participants to rate the credibility of fake news stories on a scale of 1 to 10, with higher numbers indicating greater belief.

1. In conceptual terms, the hypothesis is that social exclusion increases belief in fake news. State the null and research hypotheses in statistical terms, and include the correct notation. [1 point]

1=experimental group, 2 control group

This is upper tail test

2. Explain why the t test for independent samples is appropriate to test the hypothesis in terms of the formula for t. [1 point]

Since we are comparing two independent groups, 5 participants in experimental group and other 5 participants in the control group, independent samples t test is appropriate.

3. Compute the means, standard deviations. [1 point]

Descriptive Statistics
group		N	Minimum	Maximum	Mean	Std. Deviation
experimental	test	5	1.00	7.00	4.6000	2.30217
	Valid N (listwise)	5
control	test	5	1.00	5.00	3.2000	1.78885
	Valid N (listwise)	5

4. Compute and interpret the effect size (d) for the differences between means using the formula in the text (p. 219). [2 points]

effect size (d) = (4.6-3.2)/(sqrt((2.30217^2+1.78885^2)/2))=0.679

The effect size is medium.

5. Compute a t test for the significance of the difference between the means of the two groups. Find the critical value of the t statistic from the appropriate table in the text, or the p value from the spss output. Compare the obtained and critical value, or compare the p value in the spss output to the alpha value for the type 1 error rate.  Summarize the results of the t test. Also include the correct notation. Are the results of the test significant, i.e., likely to be found in the population? Why or why not? Should you reject or retain the null hypothesis? [4 points]

Group Statistics
	group	N	Mean	Std. Deviation	Std. Error Mean
test	experimental	5	4.6000	2.30217	1.02956
	control	5	3.2000	1.78885	.80000

Independent Samples Test
		Levene's Test for Equality of Variances		t-test for Equality of Means
		F	Sig.	t	df	Sig. (2-tailed)	Mean Difference	Std. Error Difference	95% Confidence Interval of the Difference
									Lower	Upper
test	Equal variances assumed	.121	.737	1.074	8	.314	1.40000	1.30384	-1.60666	4.40666
	Equal variances not assumed			1.074	7.540	.316	1.40000	1.30384	-1.63891	4.43891

The calculated p = 0.314 which is two sided. For one sided test, P = 0.314/2 = 0.157

The calculated P= 0.157 which is > 0.05 level of significance. Ho is not rejected.

There is no evidence to conclude that that social exclusion increases belief in fake news.

6. Summarize the results in terms of the conceptual hypothesis and variables. Explain why you think the results have practical meaning (or not). Refer to both t and d in your answer. [1 point]

  

The 5 participants in the experiment group (M = 4.6, SD = 2.3) and the 5 participants in the control group (M = 3.2, SD = 1.8), demonstrated no significant difference in belief (t[8] = 1.07, p = .157); the effect size d = 0.679,which is medium.