Ch 4 - Stat

range, standard deviation, and variance

3 different measures of variability

deviation

distance from the mean

unbiased

dividing by n − 1 produces a sample variance that provides an ____ estimate of the corresponding population variance.

variance

equals the mean of the squared deviations

degrees of freedom or df

for a sample of n scores, the ___ for the sample variance are defined as df = n-1.

bias

fortunately, the ___ in sample variability is consistent and predictable, which means it can be corrected

harder

if variability is high (large), the difference is ___ to see

easier

if variability is low, the difference is ___ to see

drawing a vertical line and labeling it

in frequency distribution graphs, how do we identify the position of the mean?

error variance

in the context of inferential statistics, the variance that exists in a set of sample data is often classified as ____

multiplied

multiplying each score by a constant causes the standard deviation to be ____ by the same constant (transformations of scale)

standard deviation

square root of the variance and provides a measure of the standard, or average distance from the mean

-S1: determine the deviation -S2: calculate the mean of the deviation scores -S3: determine the variance -S4: determine the standard deviation

steps for determining standard deviation

the number of scores in the sample that are independent and free to vary

the degrees of freedom determine what?

rang

the distance covered by the scores in a distribution, from the smallest score to the largest score

interval or ratio scales

the mean, standard deviation, and variance should be used only with numerical scores from ____ of measurement

distance

variability is defined in terms of ____

mean (central tendency) and the standard deviation (variability)

with numerical scores the most common descriptive statistics are the ____, which are usually reported together.

SS or sum of squares

___ is the sum of the squared deviation scores

variability

___ provides a quantitative measure of the differences between scores in a distribution and describes the degree to which the scores are spread out or clustered together

-V describes the distribution -V measures how well and individual score (or group of scores) represents the entire distribution

a good measure of variability serves what two purposes?

biased

a sample statistic is ___ if the average value of the statistic either underestimates or overestimates the corresponding population parameter.

biased

a sample statistic is said to be ___ if, on the average, it consistently overestimates or underestimates the corresponding population parameter.

unbiased

a sample statistic is unbiased if the average value of the statistic is equal to the population parameter. (the average value of the statistic is obtained from all the possible samples for a specific sample size, n.)

does not

adding a constant to each score ____ change the standard deviation (transformations of scale)

difficult

as the error variance increases, it becomes more ___ to see any systematic differences or patterns that might exist in the data.

a line or arrow drawn from the mean outward for a distance equal to the standard deviation and labeled

because the standard deviation measures distance from the mean, how do we identify it in a frequency distribution graph?