ch. 3 Variability

Which of these is the correct range for the following scores? 3, 6, 2, 9, 5, 5, 9.

7

unbiased estimate

A conservative estimate of a population parameter. are appropriate if your intent is only to describe the characteristics of the sample.

When computing variance, which of these is an accurate statement about the sum of the deviations?

It will always be zero.

Which of the following represents the average amount of variability in a set of scores?

SD

Which element of the formula is modified when computing standard deviation for the population?

The denominator (dividing by n-1)

When assessing variance, the individual score minus mean score provides what information?

deviation

inclusive range

inclusive range counts both the high and low scores as being among the values in the range. is the highest score minus the lowest score plus 1 (or h − l + 1).

mean deviation (also called the mean absolute deviation)

is the sum of the absolute value of the deviations from the mean divided by the number of scores

In order to calculate the standard deviation, what must you calculate first?

mean

r=h-l

r= range h=highest score l= lowest score

Which of the following is the simplest measure of variability to calculate?

range

What are the three most common measures of variability?

range, standard deviation, variance

Variability

reflects how much scores differ from one another. (also called spread or dispersion)

standard deviation

represents the average amount of variability in a set of scores. it's the average distance of each score from the mean. The larger the standard deviation, the larger the average distance each data point is from the mean of the distribution and the more variable the set of scores is. s=SD ∑=find the sum x= each individual score X¯=mean of all scores n=samples size

When computing the standard deviation, statisticians eliminate the negative numbers by

squaring the score

What is the most frequently used measure of variability?

standard deviation

The difference between computing variance and standard deviation is _______________.

taking the square root of the score that results from the division step

range (exclusive range)

the distance of the biggest score from the smallest score. computed by subtracting the lowest score in a distribution from the highest score in the distribution. r= h-l

variance

third measure of variability, the variance, is simply the standard deviation squared.