Confidence Intervals - Proportions

Construct a Proportion Confidence Interval and Objective Construct a Proportion Confidence Interval and Find Sample Size.

Can Estimate Population Parameters from Sample Statistics Relevance Can Estimate Population Parameters from Sample Statistics

Remember……

If x = the number of successes and n = the number of trials then Remember in our bean lab, a success was getting an albino bean. The proportion was successes to total number of beans

Finding the sample proportion if not given…… In a survey of 250 households, 178 had radios.

Proportion Confidence Interval……

Example…… A sample of 200,000 was taken on most popular boat names. 6% are named “Osprey.” Find a 95% confidence interval of the true proportion of boats named “Osprey.”

Answer……

Example…… In a sample of 1001 U.S. adults, 58% think that airplanes are the safest mode of transportation. Construct a 99% confidence interval.

Answer……

Example…… A sample of 500 nurses included 60 men. Find the 90% confidence interval of the true proportion of men who applied to the nursing program.

Answer……

Confidence Intervals - Proportions Finding Sample Size

Finding Sample Size of a Proportion…… Formula:

Example…… Estimate with 95% confidence the number of people who own a home computer. A previous study showed that 40% of those interviewed had a computer at home. The researcher wishes to be accurate within 2% of the true proportion. Find the minimum sample size necessary.

Answer…… Values: Plug In:

You Try…… A researcher wishes to estimate the proportion of executives who own a car phone. A previous study showed that 50% owned a car phone. She wants to be 90%confident and be accurate to within 5% of the true proportion. Find the minimum sample size necessary.

Answer…… Values: Plug In: