IntroStat-2nd test cheat sheet

# IntroStat-2nd test cheat sheet - -mean proportion and...

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-mean, proportion, and variance are unbiased estimators -List possible samples and find means. The # of books sold over course of 4 day book fair were 139, 199, 241, 61. Assume sample size of 2 randomly selected w/replacement Samples: 139-139, 139-199, 139-241, 139-61, 199-139, 199-199, 199-241, 199-61, 241-139, 241-199, 241-241, 241-61, 61-139, 61-199, 61-241, 61-61 Means: 139, 169, 190, 100, 169, 199, 220, 130, 190, 220, 241, 151, 100, 130, 151, 61 -a point estimate is a single value used to approximate a population parameter. The sample mean x bar is the best point estimate of µ because 1) for many populations, the distribution of sample means has less variation than other measures of central tendency, and 2) sample means tend to center about the population mean, not to systematically overestimate or underestimate µ -in the formula E= zα2∙σn you can replace σ with s if provided that n>30. If n ≤30 the population must be normal and σ must be used in the formula -to determine whether to use the z or t distribution in computing the margin of error, E=
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