Since everything is a reflection of our minds,

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Presentation transcript:

Since everything is a reflection of our minds, everything can be changed by our minds.

Inferences about Population Variances Sections 7.1 to 7.3 The distribution of s^2 Tests for equal variances

The Distribution of S^2 Let Y1, Y2, …, Yn be a random sample from a normal population with mean m and variance s^2. The definition of s^2: The distribution of s^2:

Estimation and Tests for s^2 (Chi-square) Confidence Interval: p.364 Chi-square Test: p.366 Normal population is required.

F Test for Equal Variances Consider two independent (random) samples from two NORMAL populations Ho: s1=s2 T.S.:

F Test for Equal Variances Ha R.R: Reject Ho if s1=s2 s1>s2 s1<s2

Example: Minitab Lab Key in the data Sample1 8.1 7.4 9.3 7.5 7.1 8.7 9.1 7.9 8.4 8.8 Sample2 3.9 4.4 3.6 4.1 4.6 3.5 4.0 4.2 4.7 Key in the data Check the normality assumption on both samples Calculate a 95% confidence interval of variance for each population Conduct a test for equal variances