Introductory Biostatistics

x¼ 47 :5mL=kg

s¼ 4 :8mL=kg

SEðxÞ¼

4 : 8

ffiffiffiffiffi

25

p

¼ 0 : 96

From Appendix C we find that thetcoe‰cient with 24 df for use with a 95%
confidence interval is 2.064, leading to a 95% confidence interval for the popu-
lation meanm(this is the population of joggers’ VO 2 uptake) of

47 : 5 Gð 2 : 064 Þð 0 : 96 Þ¼ð 45 : 5 ; 49 : 5 Þ

Example 4.5 In addition to the data in Example 4.4, we have data from a
second sample consisting of 26 nonjoggers which were summarized into these
statistics:

n 2 ¼ 26

x 2 ¼ 37 :5mL=kg

s 2 ¼ 5 :1mL=kg

SEðxÞ¼

5 : 1

ffiffiffiffiffi

26

p

¼ 1 : 0

From Appendix C we find that thetcoe‰cient with 25 df for use with a 95%
confidence interval is 2.060, leading to a 95% confidence interval for the popu-
lation meanm(this is the population of joggers’ VO 2 uptake) of

37 : 5 Gð 2 : 060 Þð 1 : 0 Þ¼ð 35 : 4 ; 39 : 6 Þ

TABLE 4.5

df

tCoe‰cient

(percentile)

5 2.571

10 2.228

15 2.131

20 2.086

24 2.064

!y 1.960

ESTIMATION OF MEANS 157