Question

In: Statistics and Probability

Data are collected from 12 randomly selected infants undergoing nutritional therapy following premature birth. The data...

Data are collected from 12 randomly selected infants undergoing nutritional therapy following premature birth. The data represent the percent gain in birthweight after 8 weeks of therapy. Generate a 95% CI for the mean percent gain in weight.

23% 32% 48% 4% 34% 20% 11% 24% 40% 69% 17% 6%

Solutions

Expert Solution

Solution:
sample mean = (23+32+48+4+34+20+11+24+40+69+17+6)/12 = 328/12 = 27.33
Sample standard deviation = sqrt(summation(Xi-Xbar)^2/(n-1))

X

(Xi-Xbar)

(Xi-Xbar)^2

23

-4.33333333333333

18.7777777777778

32

4.66666666666667

21.7777777777778

48

20.6666666666667

427.111111111111

4

-23.3333333333333

544.444444444444

34

6.66666666666667

44.4444444444445

20

-7.33333333333333

53.7777777777778

11

-16.3333333333333

266.777777777778

24

-3.33333333333333

11.1111111111111

40

12.6666666666667

160.444444444444

69

41.6666666666667

1736.11111111111

17

-10.3333333333333

106.777777777778

6

-21.3333333333333

455.111111111111

Summation

3846.66666666667

Standard devaition = sqrt(3846.66/11) = 18.7

95% confidence interval is
27.33 +/- talpha/2 * SD/sqrt(n)
27.33 +/-2.20*18.7/sqrt(12)
27.33 +/-11.87
so 95% confidence interval is
15.45% TO 39.21


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