Question

Give me exact rounded answer and please give me the right answer. Lately, I've been getting false answers!

Section two is from a different question but asking the same thing from this question

a. The best point estimate is 144.89 lb. (Type an integer or a decimal.) b. The 90% confidence interval estimate is 136.75 lb<< 153.03 lb. (Round to two decimal places as needed.)

Answer 1

Solution :

Given that,

Point estimate = sample mean = $\bar x$ = 148.82

Population standard deviation =   $\sigma$ = 31.94

Sample size = n =45

At 95% confidence level the z is ,

$\alpha$ = 1 - 95% = 1 - 0.95 = 0.05

$\alpha$ / 2 = 0.05 / 2 = 0.025

Z_$\alpha$/2 = Z_0.025 = 1.96   ( Using z table )

Margin of error = E = Z$\alpha$/2 * ( $\sigma$ /$\sqrt$n)

= 1.96 * ( 31.94 /  $\sqrt$45 )

E= 9.3322
At 95% confidence interval estimate of the population mean
is,

$\bar x$ - E < $\mu$ < $\bar x$ + E

148.82-9.3322 <  $\mu$ < 148.82+9.3322

139.49<  $\mu$ < 158.15'

139.49,158.15

Point estimate = sample mean = $\bar x$ = 148.82