Question

A university lecturer in History hypothesizes that more time studying predicts better exam performance. Before the next exam, the lecture asks students in the class the average amount of time (in minutes) they spend in the library per day. The data are below. What can be concluded with α = 0.05?

time	exam
41 25 48 58 66 81 95 101 121 97 81 111	75 75 69 72 63 60 66 57 60 70 65 65

a) What is the appropriate statistic?
---Select--- na Correlation Slope Chi-Square
Compute the statistic selected above:  

b) Compute the appropriate test statistic(s) to make a decision about H₀.
(Hint: Make sure to write down the null and alternative hypotheses to help solve the problem.)
Critical value =  ; Test statistic =  
Decision:  ---Select--- Reject H0 Fail to reject H0

c) Compute the corresponding effect size(s) and indicate magnitude(s).
If not appropriate, input and/or select "na" below.
Effect size =  ;   ---Select--- na trivial effect small effect medium effect large effect

d) Make an interpretation based on the results.

Students who spend more time studying have better exam performance.Students who spend more time studying have worse exam performance.    Students time studying does not predict exam performance.

Answer 1

a) What is the appropriate statistic?
Correlation

(b)

Following table shows the calculations:

	Time, X	Exam, Y	X^2	Y^2	XY
	41	75	1681	5625	3075
	25	75	625	5625	1875
	48	69	2304	4761	3312
	58	72	3364	5184	4176
	66	63	4356	3969	4158
	81	60	6561	3600	4860
	95	66	9025	4356	6270
	101	57	10201	3249	5757
	121	60	14641	3600	7260
	97	70	9409	4900	6790
	81	65	6561	4225	5265
	111	65	12321	4225	7215
Total	925	797	81049	53319	60013

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(b)

(c)

Since results are not significant so effect size is not necessary.

Effect size =na

(d)

Students who spend more time studying have worse exam performance.