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# Noteevenn30youshouldstillusetifthe isunknown slide 21

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Unformatted text preview: sampling 1 will be of the form x ± . If the standard deviation is greater than 6 inches the actual interval will be wider than +/-1. Slide 20 Interval Estimation of a Population Mean: Small­Sample Case (n < 30) s s s If the variable of the population is not normally distributed: • The only option is to increase the sample size to n > 30 and use the large­sample interval­estimation procedures. If the variable of the population is normally distributed and σ is known: • The large­sample interval­estimation procedure can be used. If the variable of the population is normally distributed and σ is unknown: • The appropriate interval estimate is based on a probability distribution known as the t distribution. • Note: Even n ≥ 30, you should still use t if the σ is unknown. Slide 21 t Distribution s s s s s The t distribution is a family of similar probability distributions. A specific t distribution depends on a parameter known as the degrees of freedom. As the number of degrees of f...
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