Answer: 
Step-by-step explanation:
The confidence interval for population mean is given by :-

Given : Sample mean :
hours
Standard deviation
hours
Sample size : n=90, which is a large sample(n<30), so we use z-test.
Significance level: 
Critical value : 
Then , the confidence interval for population mean will be :-

Hence, the 90% confidence interval for the mean life
of all light bulbs of this type. is 
Answer:
37.7
Step-by-step explanation:
The formula is C = 2 • 3.14 • r , you multiply the radius by pi/3.14, then you multiply that by product by 2.
Answer:
(a) S=
(B) S(average speed)=65.04
Step-by-step explanation:
Given
D=S*T
So, S=
and
T=11.5 Hr
D=748 Km.
S(average speed)=
=65.04 kmph
Answer:
search it up :)
Step-by-step explanation: