Business Statistics

296 Business Statistics

Solution Here, s = . E = 2.4

Sample size for estimating population mean

m

2 2

2

2

z

n

E

α

×

=

s

2 2

2

(1.96) (4.2)

(2.4)

n

×

=

3.8416 17.64 67.76

11.76 12

5.76 5.76

×

= =

=

=n

Approximately

Thus, a sample size n = 12 should be taken to estimate the population mean

with 95% condence interval and given standard deviation and sample error.

9.7.4 Sample Size for Estimating Population Proportion p

The method of determining the sample size for estimating the population proportion p is similar to the

method we have discussed for determining the sample size for estimating population mean

m. The z

formula for sample proportion is

−

=

p p

z

pq

n

The difference ...