Chap 2 Measure of Central Tendancy Flashcards
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.
Define Central Tendency
A set of distribution characteristics that interests the researchers. This set consists of the mean, median and mode.
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
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
Define Mode (used least)
The score in the distribution that occurs most frequently.
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.
Define Statistic:
A value derived from the data collected from a sample
Define Parameter:
A value derived from the data collected from a population, or the value inferred to the population fro a sample statistic
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
Define Multimodal:
When a distribution of scores that has 2 or more values that have the highest frequency scores.
Define Bimodal:
A distribution that has 2 values that have the highest frequency scores
Define Sample:
An individual or group, selected from a population, from whom or which data is collected
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.
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.
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.
