Exam 4: Measures of Central Tendency and Variability

We use N - 1 in the denominator of the equation for calculating the sample standard deviation because it provides us with an accurate estimate of the population standard deviation.

If the number of raw scores is odd, the median is always the score in the middle position.

The symbol Σ S stands for sum of squares.

Given the following set of scores X : 10, 12, 6, 8, 9, 11, 13, 13, 5, 0, 1 What is the mean?

A history professor gives a quiz to his class and records the following scores: 13, 11, 11, 9, 12, 13, 16, 14, 11, 10, 8, 13, 20. The mode(s) for this distribution is(are) _________.

A distribution has a mean of 78 and a median of 92. This distribution is _________.

If one knows ΣX , N , and ΣX ², one can calculate both the variance and the standard deviation. It is not necessary to know the mean itself.

By changing the value of one score in a sample this will necessarily cause the median to change.

The most commonly encountered measure of variability is _________.

Given the following sample scores on an aptitude test? 30, 20, 15, 19, 16

If the following scores were population scores X : 10, 12, 6, 8, 9, 11, 13, 13, 5, 0, 1 What would the standard deviation be?

The mean number of students in a classroom at school A is 32.5 and there are 25 classrooms. The mean number of students at school B is 29.6 in 12 classrooms. At school C the mean in each class is 15.3 for 10 classrooms. What is the mean number of students per classroom for all the schools combined?

The variance is the square of the standard deviation.

The overall mean does not take into account the different number of subjects in each group.

Repeat the above analysis on the original data in problem 27; this time multiply each original value by 4. The resulting data are: Miles per gallon: 124.8, 114.4, 145.6, 149.2, 120.4, 116.0, 130.8, 127.6

The formula for the population standard deviation is

The equation for standard deviation is the same regardless of whether the scores are of a sample or a population.

Central tendency describes the central location of the set of scores.

Which of the following is not a property of the mean?

For data that are not normally distributed, the standard deviation will sometimes be negative.