WEEK 10: Descriptive statistics

Question 1

Measures of central tendency
the equation for mean?
The first step to calculating the median?

Answer 1

mean (equation for the mean- sum/ number in total)
mode
median (order the numbers first smallest to largest)

Question 2

Normal distribution curve
Where are the mean, mode and median placed on the curve?

Answer 2

mean, mode and median all equal

Question 3

The negatively skewed distribution curve
Placement of mean, mode, and median?
Direction of curve?

Answer 3

mode is higher than the mean
eg more students scored higher than the mean
Negative direction- right to left

Question 4

The positively skewed distribution curve
Direction?

Answer 4

Positive direction- left to right
Less students scored above average

Question 5

Measures of dispersion (spread)
What does dispersion describe? (distance from?)

Answer 5

Dispersion describes the distance from the average

Question 6

Measures of dispersion (4)
Type of range? Percentile range?
The standard deviation is the square root of the?
What does a large variance/standard deviation show?

Answer 6

Range
Interquartile range: the difference between the 75th and 25th percentile
Variance
Standard deviation: the average deviation of the scores from the mean (square root of variance)

The larger the variance/standard deviation, the further away the scores are from the mean

Question 7

How to choose which measures of central tendency to use
What should all of the measures of central tendency indicate from a data set? Therefore how do you choose the best measures of central tendency?
-How to find out which measures of central tendency is the best for the data set (compare?)
What is the most frequently used measures of central tendency?

Answer 7

Any of the central measures of the tendency should indicate the average score in the sample so it depends on so what kind of measures of central tendency you choose to use depends on the data
In order to see if the measures of central tendency you have chosen is the best one to represent the typical score in the data set, compare the calculated measure of central tendency with the scores in the sample to see if it is representative

Typically the mean is one of the most frequently used measures of central tendency

Question 8

Why is the mean the most frequently used measure of central tendency?
What kind of scores is the mean calculated from? not from? (2) (related to which two measures of central tendency?)
What is the downside to using the mean as a representative for the data set? (can be affected by?)

Answer 8

Compared to the other measures of central tendency, the mean is the best indicator as it is calculated from the actual scores, not from the ranks (median) or from the frequency of occurrence (mode)

However, a downside to using the mean in order to represent a data set is that the calculation can be skewed by extreme scores, therefore, making the calculated mean not representative.