Question

11.
A company claims that the mean life of its electric light bulbs is
28 months. A random sample of 10 bulbs has the following life in
months.
26
24
32
28
20
20
23
34
30
Test the claim of the company at 5% level of significance
​

Answer 1

Given :  A company claims that the mean life of its electric light bulbs is

28 months.

A random sample of 10 bulbs has the following life in  months.

26

24

32

28

20

20

23

34

To Find : Test the claim of the company at 5% level of significance

Solution:

Sample of only 9 Bulbs is given

Hence Data is Incomplete

Procedure

Find Sample mean  

Find Sample Standard Deviation

Population mean  = 28  month

n = 10  sample size

Find t score

= ( Sample mean - Population mean )/( Sample Standard Deviation/√sample size))

for 5 % level of significance for 9 degree of freedom check required  value

t for 5 % level for 9 degree of freedom = 2.263

if  | t |  > 2.263  rejected

if  | t |   < 2.263  not rejected

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