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# T test for Significance of correlation & Scatter plot

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Instructions for Exercises 12.2 and 12.3:

(a) Make an Excel scatter plot. What does it suggest about the population correlation between X and Y?

(b) Make an Excel worksheet to calculate SSxx , SSyy , and SSxy . Use these sums to calculate the sample correlation coefficient. Check your work by using Excel's function =CORREL(array1,array2).

(c) Use Appendix D to find t.05 for a two-tailed test for zero correlation.

(d) Calculate the t test statistic. Can you reject &#961; = 0? (e) Use Excel's function =TDIST(t,deg_freedom,tails) to calculate the two-tail p-value.

Chapter 12 Bivariate Regression 497
12.2 Part-Time Weekly Earnings (\$) by College Students WeekPay
Hours Worked (X) Weekly Pay (Y)
10 93
15 171
20 204
20 156
35 261

12.3 Data Set Telephone Hold Time (min.) for Concert Tickets CallWait
Operators (X) Wait Time (Y)
4 385
5 335
6 383
7 344
8 288