# T test for Significance of correlation & Scatter plot

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 ρ = 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

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#### Solution Summary

The solution provides step by step method for the calculation of sum of squares of x and y, sample correlation and test statistic for significance of correlation coefficient. Formula for the calculation and Interpretations of the results are also included.