Amarketing firm is asked to estimate the percent of existing customers who would purchase a "digital upgrade" to their basic cable tv service. the firm wants 85 percent confidence and an error of ± 5 percent (i. e. 0.05). what is the required sample size (to the next higher integer)?

208

Step-by-step explanation:

When prior estimate of population proportion is not available , then the formula for sample size:  

, wherez*= critical-value.

E= Margin of sampling error.

Let p be the population proportion of existing customers who would purchase a "digital upgrade" to their basic cable TV service.

As per given , we have

E= ± 5 percent= ± 0.05

Using z-table , the critical z-value corresponding to 85% confidence level = z*=1.439

Then, the required sample size  :

[Rounded to next integer.]

Thus, the required sample size = 208

look at the picture.

y-intercept for the function on a picture is 4 → point (0, 4).

y-intercept for the function

is for x = 0. substitute:

y-intercept is 8 → point (0, 8).