H355 quiz 2

What is the multiplier for the approximate 95% rule?

2

If the mean for a group equals 40 and the standard deviation equals 5, what percentage of the cases in a normal distribution lies between 40 and 45?

34%

Interquartile Range (IQR)

the range of the middle 50% of the data

formula for standard deviation

the square root of the variance

Variance

The average of the squared differences from the mean.

Variability

The differences among scores

To two decimal places, what is the standard deviation of these scores: 3, 5, 6, 7, 8

1.72

How to calculate variance

1. Calculate the mean 2. For each number: subtract the mean and square the result 3. Workout the average of those squared differences

What is the multiplier for the 99.7% rule?

3

To two decimal places, what is the standard deviation of these scores: 0, 2, 5, 9, 12

4.41

What is the interquartile range of these scores: 10, 10, 11, 12, 13, 13, 14, 14, 15, 17, 18, 18

4.5

For all practical purposes, the normal curve has how many standard deviation units?

6

If the mean for a group equals 27 and the standard deviation equals 3, what percentage of the cases in a normal distribution lies between 24 and 30?

68%

Outliers

Numbers that are much greater or much less than the other numbers in the set

You and your friends have just measured the heights of your dogs. The heights (at the shoulders) are: 600mm, 470mm, 170mm, 430mm, and 300mm. What is the mean, variance, and standard deviation?

Mean (average) height: 394mm Variance: 21,704 SD: 147 (to the nearest mm)

The interquartile range is associated with which average?

Median

If everyone in a population has the same score, what is the value of the standard deviation for those scores?

Zero

standard deviation

a measure of how spread out numbers are; how much scores differ (or vary) from their mean.

synonyms for variability

spread and dispersion

range

the difference between the highest and lowest scores in a distribution (subtracting the lowest score from the highest score)