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EXSS 254 Final
Terms in this set (72)
Characteristics of a normal distribution
Bell-shaped curve, symmetrical distribution about vertical axis of the curve (mirrored), greatest number of scores in middle of curve, and all measures of central tendency are at the vertical axis
Groups of individuals who are very similar in ability and curve is pointed, homogeneous
If group consists of individuals with a wide range of ability, curve is flat, heterogeneous
Group of scores has two modes, the curve has two high points
A curve with scores clustered at one end
Most generally used measure of central tendency, arithmetic average of distribution of scores
Mean is calculated by
Summing all the scores and dividing by total number of scores
Most sensitive of all measures of central tendency
Most appropriate measure of central tendency to use for ratio data and may be used on interval data
Considers all information about the data and is used to perform other important statistical calculations
Influenced by extreme scores
The sum of
The total number of scores in a distribution
Formula for calculating mean
The score that represents the exact middle in the distribution, 50th percentile
Not affected by extreme scores
Is a measure of position
Not used for additional statistical calculations
Steps for calculation of median
1. Arrange scores in ascending/descending order
2. Multiply N by 0.50 to find 50% distribution
3. If number of scores is odd, P50 is middle score
4. If number of scores is even, P50 is average of two middle scores
Score that occurs most frequently
The least used measure of central tendency
Not used for additional statistical calculations
Not affected by extreme scores, the total number of scores, or their distance from center of distribution
The mean, median, and mode are the same for..
The farther away from the mean and median the mode is, the less _____ the distribution
In a negatively skewed curve, the scores are clustered at the ____ end of the scale
In a positively skewed curve, the scores are clustered at the ____ end of the scale
The spread or scatter of scores; also known as dispersion or deviation
The measures of variability are..
Range, quartile deviation, and standard deviation
Determined by subtracting the lowest score from the highest score
Dependent of two extreme scores
Indicates nothing about the variability of the scores
Least useful measure of variability
R= High score - Low score
The spread of the middle 50% of the scores around the median
Uses the 75th percentile and 25th percentile to determine deviation
Indicates amount that needs to bee added to and subtracted from the median to include middle 50%
Usually is not used in additional statistical calculations
Steps for calculating Q3
1. Arrange scores in ascending order
2. Multiply N by 0.75 to find 75% of distribution
3. Count up from the bottom score to the number determined in step 2.
Most useful and sophisticated measure of variability, describes the scatter of scores around the mean, more stable
It is the square root of the variance, which is average of the squared deviations from the mean
Is applicable to interval and ratio level data, includes all scores, and is most reliable measure of variability
Used with the median
A relatively small standard deviation indicates that the group being tested has little variability or much variability
Used to perform other statistical calculations
Standard Deviation symbol
Deviation score symbol
Individual score symbol
Standard deviation formula
A point in the distribution of scores below which a given percentage of the scores fall
The percentage of the total scores that fall below the given score, indicates the position of a score in a distribution in percentage terms
Represents the number of standard deviations by which a raw score deviates from the mean
Has a mean of 50 and a standard deviation of 10. May extend form 0 to 100 but is unlikely that it would fall below 20 or above 80
A statistical technique used to express the relationship between two sets of scores
Degree to which a straight line best describes the relationship between two variables.
Number that represents the correlation
The values always range from +1.00 to -1.00
A positive coefficient indicates ____ relationship.
A negative coefficient indicates ____ relationship.
A correlation of or very close to .00 indicates ___ relationship.
A correlation of or very close to 1.00 indicates ____ relationship
Graph used to illustrate the relationship between two variables
Preparing a scattergram
1. Determine range
2. Designate one variable as X and one as Y
3. Draw and label axes
4. Plot each pair of scores on the graph by placing a point at the intersection of the two scores
Predicts there will be a difference in the alternative hypothesis.
Degrees of Freedom
Concept is used in all statistical tests
Level of Significance
Probability of rejecting a null hypothesis when its true. Two most common levels are 0.05 and 0.1.
Standard Error of the Mean
Standard Error of the Mean..
The standard deviation of the sampling distribution
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