Читать книгу Student Study Guide to Accompany Statistics Alive! - Wendy J. Steinberg - Страница 25

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2 The sum of the deviations is 0.00. Variance = 126.99 (using N) or 133.67 (using n − 1); standard deviation = 11.27 (using N) or 11.56 (using n − 1).

3 The highest grade is approximately 1.20 standard deviations above the mean. The lowest grade is approximately 1.7 SD below the mean.

4 The new variance = 145.64 (using N) or 153.31 (using n − 1). The new standard deviation = 12.07 (using N) or 123.38 (using n − 1).

5 The variance was the most affected by this change.

6 Three scores: 98, 99, and 99.

7 The variance = 6.60 (using N) or 7.33 (using n − 1). The standard deviation = 2.57 (using N) or 2.71 (using n − 1).

8 The new standard deviation would be 2.42 (using N) or 2.52 (using n − 1).

9 There are seven scores that fall within 1 SD above and below the mean.

10 You would use the formula with n − 1 in the denominator because the sample size is less than 30. The estimated population variance would be 7.33.

11 The first mean is more representative because the scores are more tightly clustered about the mean.