-
What is the mode?
The most commonly occurring value in the data set
-
What is the median?
- A value that divides the sample scores into two halves
- Equal numbers of scores lie above and below the median
-
How might one find the median for a data set?
- For an odd number of figures, take the middle value
- For an even number, take the middle two, add them and then divide the total by 2
-
How might one calculate the arithmetic mean?
Find the sum of all values and divide that figure by the number of values
-
What do Y values represent?
The scores for data sets
-
What does Y (bar) represent?
The mean of values in the data set
-
What does ∑ represent?
- The operation of addition
- (∑Y: add up all Y values)
-
How can the mean be said to be a balance point?
The sum of distances before the mean is equal to the sum of distances after it
-
If the variable is categorical, what is the most appropriate measure of central tendency?
The mode
-
If the distribution is normal (symmetrical with no outliers) what is the most appropriate measure of central tendency?
The mean
-
What effects does a positive skew have on measures of central tendency?
- The mode stays the same
- The median score increases (higher than the mode)
- The mean score increases (higher than the median)
-
What effects does a negative skew have on measures of central tendency?
- The mode stays the same (for the distribution of scores)
- The median score decreases (lower than the mode)
- The mean score decreases (lower than the median)
-
What are the relevant sensitivities of the mean?
- Sensitive to the exact values of all scores in the distribution
- Very sensitive to extreme scores (outliers)
- More sensitive than the median to outliers or legitimate data points that lie on the fringes
-
What are quartiles?
Divisions of data into quarters
-
What are the tree quartiles?
- Lower quartile: Divides the first 25% of the scores from the upper 75%
- Median: Divides the first 50% from the second half
- Upper quartile: Divides the fist 75% from the upper 25%
-
What is the range?
- The difference between the highest and lowest scores
- It is only based on two scores, however and is unstable and vulnerable to outliers
-
What is the interquartile range?
- The difference of the values of the third and first quartile
- Q3-Q1
- Sometimes called the midrange as it it the range of the middle 50% of scores
-
What are the deviation scores?
The value of the Y scores minus the mean
-
What is the mean of deviation scores?
- 0
- This is because the scores always sum to 0
-
What are absolute deviations?
- The removal of minus signs from the deviation scores
- This is valid, but is rarely used
-
What is the variance?
- The degree of dispersion of results around the mean
- Each score is represented as a deviation and dispersion is measured in terms of the size of deviation
-
What is the sum of squares?
- The sum of the squared mean values
- SS= ∑[Y-Y(bar)](squared)
-
What is the variance?
- The sum of squares divided by the number of results -1
- n-1 is known as the degrees of freedom
-
What is the standard deviation in relation to variance?
The square root of the variance value
-
Why is the standard deviation better than the variance?
It is in the same units of measurements as the original score
-
What us the symbol for variance?
s(squared)
-
What is the symbol for standard deviation?
s
|
|
