Question

Question 14 1 pts We draw a random sample of size 25 from a normal population with variance 2.2. If the sample mean is 18.5, what is a 90% lower limit confidence interval for the population mean?

Answer 1

Question 14) Given that, population variance = 2.2

(o

sample size (n) = 25 and sample mean $(\bar x)$ = 18.5

Since, population variance is known, we used the standard normal distribution.

A 90% confidence level has significance level of 0.10 and critical value is,

Za/2 = 1.645

The lower limit of the 90% confidence interval for the population mean is,

Lower Limit = 7 - Za/2 n

V2.2 => Lower Limit = 18.5 – 1.645 * 25

$=>\text { Lower Limit } = 18.5 - 1.645 *\sqrt {\frac {2.2}{25} }$

$=>\text { Lower Limit } = 18.5 -0.4880$

$=>\text { Lower Limit } = 18.0120$

=> Lower Limit = 18.0120