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Chapter 9
Key Ideas and Words
Section 9.1
ο‚· Point estimate
o statistics vs. parameter
o point estimate for population proportion p is ̂𝑝 = 𝑛
o p may also represent a probability of a binomial distribution, such as p=0.5 for a fair
ο‚· Confidence interval for an unknown parameter
ο‚· Margin of error
ο‚· Interpretation of what is meant by being β€œ95%” confident (think simulations
ο‚· Formula for confidence interval for population proportion, p.
ο‚· Know z-multipliers for 90%, 95%, and 99% confidence intervals.
ο‚· Requirements: Minimum sample size and sample size very small relative to population size.
o np(1-p) >= 10
o n <= 0.05N, N=population size
ο‚· Calculating sample size to obtained desired margin of error E.
o Using educated guess for population proportion.
o Using p=0.5 for conservative (large) sample size.
o Round up to nearest integer.
Section 9.2
ο‚· Point estimate for population mean is the sample mean
ο‚· Distribution of z-score for sample mean using sample standard deviation, S, instead of
population standard deviation, 𝜎.
ο‚· Student’s t-distribution
o Degrees-of-freedom
o t-table
ο‚· t-distribution vs. standard normal (Z) distribution
ο‚· Formula for confidence interval for population mean πœ‡
ο‚· How to calculate approximate sample size to get desired margin of error E.
o Note: This calculated n is likely too small because z-value < t-value