Question

With 90 percent confidence, for sample mean 342.50, sample standard deviation 12.60, and sample size 35, what is the upper confidence limit with 2 decimal places?

Answer 1

Solution :

Given that,

= 342.50

s = 12.60

n = 35

Degrees of freedom = df = n - 1 = 35 - 1 = 34

At 90% confidence level the t is ,

= 1 - 90% = 1 - 0.90 = 0.1

  = 0.1

t _,df = t_0.1,34 =1.307 (from table)

Margin of error = E = t_,df * (s /n)

= 1.307 * (12.60 / 35) = 2.78

The 90% upper confidence limit is

+ E

342.50 + 2.78

345.28

upper confidence limit   345.28