Question

In Born together—Reared apart: the Landmark Minnesota twin study (2012), Nancy Segal discusses the efforts of research psychologists at the University of Minnesota to understand similarities and differences between twins by studying sets of twins who were raised separately. The Excel Online file below contains critical reading SAT scores for several pairs of identical twins (twins who share all of their genes), one of whom was raised in a family with no other children (no siblings) and one of whom was raised in a family with other children (with siblings). Construct a spreadsheet to answer the following questions.

Open spreadsheet

a. What is the mean difference between the critical reading SAT scores for the twins raised with no siblings and the twins raised with siblings?

(to 2 decimals)

b. Provide a 90% confidence interval estimate of the mean difference between the critical reading SAT scores for the twins raised with no siblings and the twins raised with siblings.

(, ) (to 2 decimals)

c. Conduct a hypothesis test of equality of the critical reading SAT scores for the twins raised with no siblings and the twins raised with siblings.

-value is  (to 4 decimals)

At , what is your conclusion?

_________Can concludeCannot conclude that there is a difference between the mean scores for the no sibling and with sibling groups.

SAT Score No Siblings	SAT Score With Siblings	Change in SAT Score (di)		Part a
415	451			After reading these instructions delete all text in this shaded area.
615	584
635	660			Use the XLMiner Analysis ToolPak to conduct your analysis.
378	437
429	457			After deleting all text in this shaded area, set the output range in
404	466			the ToolPak to the top left cell of this area (E2).
528	425
646	583			Your analysis output should fit into this shaded area.
517	486
695	652
583	484
607	650
521	468
633	574
545	465
592	673
528	523
612	650
502	509
596	649
				Part b
				The 90% confidence interval
				C.I.Lower Limit
				C.I.Upper Limit
				Part c
				Degrees of Freedom
				Test statistic
				p-value
				Significance Level (Alpha)	0.01
				Can we conclude that there is difference between the mean scores? (Enter "Can conclude" or "Cannot conclude")

Answer 1

a)

difference = 6.8

b)

90% CI for mean difference: (-15.5, 29.0)

c)

Degrees of Freedom	= 20-1 = 19
				Test statistic   = 0.53
				p-value
				= 0.605
				Significance Level (Alpha)	0.01
				Can we conclude that there is difference between the mean scores? (Enter "Can conclude" or "Cannot conclude")

T-Test of mean difference = 0 (vs ≠ 0): T-Value = 0.53 P-Value = 0.605

d)

we can't conclude