Software millionaires and birthdays. Refer to the analysis of the disproportionate number of software millionaires who were born around the year 1955, Exercise 11.112 (p. 683). Recall that on his Web blog (www .measuringusability.com), statistical consultant Jeff Sauro investigated this question by analyzing the data shown in the accompanying table. Decade Total US Births (millions) Number of Software Millionaire Birthdays Number of CEO Birthdays (in a random sample of 70 companies from the Fortune 500 list) 1920 28.582 3 2 1930 24.374 1 2 1940 31.666 10 23 1950 40.530 14 38 1960 38.808 7 9 1970 33.309 4 0 From “Were most software millionaires born around 1955?” by Jeff Sauro in Measuring Usability. Copyright © 2010 by Measuring Usability LLC. Used by permission of Measuring Usability LLC.

a. Compute Spearman’s rank correlation coefficient, rs, relating number (y) of software millionaire birthdays in a decade to total number (x) of US births.

b. Refer to part

a. Is there evidence of positive rank correlation between y and x? Test using a = .05.

c. Compute Spearman’s rank correlation coefficient, rs, relating number (y) of software millionaire birthdays in a decade to number (x) of CEO birthdays.

d. Refer to part

c. Is there evidence of positive rank correlation between y and x? Test using a = .05.