Descriptive statistics

Question 1

Frequency Distribution

Answer 1

A count of the number of occurrences of each different value in the data set

Question 2

Two steps to make a frequency distribution

Answer 2

1. count the number of occurrences (frequency) of each value of the dependent variable
2. Make a graph

Question 3

Class interval

Answer 3

Clusters of data when there is a large range of values

Question 4

Exact limits

Answer 4

The limits continuous variables fall between. They are half a unit below and half a unit above the values of the class intervals

Question 5

Normal distribution

Answer 5

A symmetric frequency distribution

Question 6

Measures of central tendency

Answer 6

summerise a data set with a single value that is representative of the data set

Question 7

Variability

Answer 7

the extend to which things are not all the same

Question 8

Measures of variability

Answer 8

measure how scores differ from one another

Question 9

Variance

Answer 9

S^2

the Sum of squared deviations from the mean decided by the number of scores

Question 10

Standard deviation

Answer 10

square root of the variance

approximately the average distance of the scores in a data set from the mean

Question 11

Inflection point

Answer 11

the point where the curve starts bending outwards

Question 12

Normal distributions inflection point

Answer 12

It is always 1 sd away from the mean

Question 13

68% of the scores of the normal distribution

Answer 13

are within +/-1sd

Question 14

96% of the scores of the normal distribution

Answer 14

are within +/-2sd

Question 15

99.7% of the scores of the normal distribution

Answer 15

are within +/-3sd

Question 16

Z-scores

Answer 16

tell us how far away a score is from the mean, taking into account the variability of the scores in the data set, expressed as the number of sd the score is away from the mean

Question 17

Area under the normal distribution curve

Answer 17

is bonded by two values and equals the relative frequency or proportion of cases between these two values

Question 18

three steps to determine the proportion of scores compared to the individual score:

Answer 18

1. calculate the Z-score
2. draw a picture of the curve
3. look up the value of Z in the Z-table to find the ralative position of the individual socre

Question 19

how is the Z-distribution obtained?

Answer 19

by converting every data element to itsZ-score

Question 20

What are the Z-distribution’s properties?

Answer 20

• it is normal
• has a mean of zero
• has sd of 1