Chap 2 Measure of Central Tendancy Flashcards Preview

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Flashcards in Chap 2 Measure of Central Tendancy Deck (25):
1

Define Distribution

A group, of scores from a sample on a single variable. Often, but not necessarily, these scores are arranged in order from smallest to larger.

2

Define Central Tendency

A set of distribution characteristics that interests the researchers. This set consists of the mean, median and mode.

3

Define Mean (average):

The arithmetic average of distribution of scores (most common)
2 different symbols are used for mean x ̅ and μ
x ̅ applies to a statistic that applies to a sample
μ - applies to a parameter that applies to a population.

To find the mean: If you have 10 scores in a distribution, you would add all the score together to find the sum then divide them by 10.

2+3+4+5+2+4+3+2+1+2= 26/10 = 2.6
Formula for Calculating the Mean of a distribution:

μ = ΣX/N or x ̅ = ΣX/n

4

Define Median ( P50)

The score in a distribution that marks the 50 percentile. It is the score at which 50% of the distribution falls below and 50% falls above.

To find the median- arrange all the numbers is a distribution in order from smallest to largest then find the middle score.
1 2 2 2 2 3 3 4 4 5 6 -if odd # distribution just find the middle #
1 2 3 4 5 6 7 8 9 10 – if even locate middle 2 # and add 5+6/2=5.5 median

5

Define Mode (used least)

The score in the distribution that occurs most frequently.

6

Define Median Split:

Dividing a distribution of scores into 2 equal groups by using the median score as a divider. Those scores above the median are "high" group whereas those below the median are the "low" group.

7

Define Statistic:

A value derived from the data collected from a sample

8

Define Parameter:

A value derived from the data collected from a population, or the value inferred to the population fro a sample statistic

9

Define Population (μ):

The group from which data are collected or a sample is selected. The population encompasses the entire group for which the data are alleged to apply

10

Define Multimodal:

When a distribution of scores that has 2 or more values that have the highest frequency scores.

11

Define Bimodal:

A distribution that has 2 values that have the highest frequency scores

12

Define Sample:

An individual or group, selected from a population, from whom or which data is collected

13

Define Skew:

When a distribution of scores has a high number of scores clustered and one end of the distribution with relatively few score spread out toward the other end of the distribution, forming a tail.

14

Define Negative Skew:

In a skewed distribution, when most of the scores are clustered at the HIGHER end of the distribution with a few scores creating a tail at the lower end of the distribution.

15

Define Postive Skew

In a skewed distribution, when most of the scores are clustered at the LOWER end of the distribution with a few scores creating a tail at the higher end of the distribution.

16

Define Outliers

Extreme scores that are more than 2 standard deviations above or below the mean.

17

Define Population (μ):

The group from which data are collected or a sample is selected. The population encompasses the entire group for which the data are alleged to apply

18

What does this symbol mean x ̅ ?

The sample mean

19

What does this symbol mean μ

The population mean

20

What does X represent?

The individual score in the distribution

21

What does n represent?

The number of scores in the sample

22

What does N represent?

The number of scores in a population

23

What does P50 represent?

Symbol for the median

24

What does Σ represent?

The sum of; to sum

25

What does ΣX represent?

The sum of X; adding up all the scores in a distribution.