VII A survey of 900 nonfatal accidents showed that 157 invol

VII. A survey of 900 non-fatal accidents showed that 157 involved the use of a cell phone. A. Determine a point estimate for p. the population proportion of nonfatal accidents that involved the use of a cell phone. B. Construct a 90% confidence interval for the proportion of non-fatal accidents that involved the use of a cell phone and interpret the interval. Interval _____________________ Interpretation: OR Why can?t it be done?

Solution

given that sample proportion = 0.1744

std dev^2 = 0.1744(0.8256)/900

std error = 0.0127

n = 900

A. Point estimate p = 0.1744

For 90%, z value is 1.64

Margin of error for 90% = 1.64(0.0127)

= 0.0208

90% conf interval lower bound = 0.1744-0.02080=0.1536

Upper bound =  0.1744+0.02080=0.1952

Interval = (0.1536,0.1952)

The mean canhave range on either side with an error of 4.26.

i.e. Proportion  can lie in this interval with 90% confidence.