Question

Construct a 90% confidence interval of the mean birth weight of 195 boys with sample mean =32.7 hg , and standard deviation =6.6 hg.

Group of answer choices

a) 1.645<mean<1.777

b) 31.923<mean<33.477

c) 32%<mean<33%

d) 0.777<mean<1

Answer 1

solution:

From the given information

Sample mean , = 32.7

Standard deviation () = 6.6

Sample size (n) = 195

For 90% confidence level , = 1 - CL = 1 - 0.90 = 0.1

Critical value : Zc = Z(/2) = Z(0.05) = 1.645 [ use Z distribution table ]

The confidence interval for population mean is given by

CI : ±  Z * ( / )

: 32.7  ± 1.645 * ( 6.6 / )

: 32.7 ± 0.777

:( 31.923 , 33.477)

: 31.923 < < 33.477

90% confidence interval of mean birth weight of 195 boys is: (31.923 , 33.477)

Therefore, Option-B is correct