Proportion
Saturday, 17 August 2019
9:32 PM
Created with Microsoft OneNote 2016.
![Example
In a random sample of 85 car engine crankshaft bearings, 10 have a surface
finish that is rougher than the specifications allow. a) Find a 95% confidence
interval on the true proportion of produced bearings that exceeds the
roughness specification.
a) The estimate of is —
n
error is
sd(P)
n
10
0.118. Thus, the estimated standard
0.118 x (1 -0.118)
- 0.035
85
and an approximated two-sided 95% confidence interval for is
= [0.118±1.96 x 0.035] - [0.049,0.186]
—+ we are 95% confident that the true proportion of produced bearings
outside specifications is between 0.049 and 0.186](Proportion_files/image004.png)