stats 150 math problem

Question

in 1980 more than 35 of cars purchased had a manual transmission by 2007 the proportion has decreased to 7.7%. a random college students who owned cars revealed the following: out of 131 cars, 21 had stick shifts. estimate the proportion of college students who drive sticks with 90% confidence . round your answers to three decimal p;aces

Answer 1

This is simple if you have a TI 83/84.

Go to Stat>Tests>A(1-PropZInt...)>Enter

Then enter n=131: x=21:C-level=.90 >Calculate

It will give the answer (.1076,.2130) rounded to 4 significant digits.

If you want the formula you can find it on numerous web sites. A good resource is Stat Trek or the Khan Academy.