MAT 117 Chapter 8: STATS Ch. 8
26 Oct 2016
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Chapter 8: estimating the value of a parameter. X x = x = / n (cid:951) (cid:950) Confidence interval: provides a range of values that, w/ a certain level of confidence, contains the population parameter of interest. Confidence interval for the pop. mean when is known: sample mean x . = & sample standard deviation x = / n where & are mean & standard deviation of pop. One important characteristic is the same size (cid:951) 25. Confidence interval for : point estimate margin error. The z-score of x is normally distributed when the mean & standard deviation of pop. is known. Then will hold the normality, but when the standard deviation is unknown, will not hold the normality. In fact, we have the picture shown below. In this case, the a / 2 = 0. 025. = ( (cid:883). (cid:888)(cid:886)(cid:887) (cid:950) (cid:1852) < 1. 645) = 0. 90: ex: the average life expectancy for bostonians is 78. 1 yrs.
