Topic 3

Question 1

What is descriptive statistics?

Answer 1

Collection of methods for CLASSIFYING and SUMMARISING data

Question 2

What are the two main types of descriptive statistics?

Answer 2

1. Measures of central tendency

2. Measures of validity

Question 3

What are frequency distributions?

Answer 3

A count of the number of occurrences of each different value in the data set

Question 4

How do you make a frequency distribution?

Answer 4

1. Count the number of occurrences (frequency) of each DV value
2. Plot the graph

X axis -> values of DV
Y axis -> frequency

Question 5

What kind of value range is a frequency distribution good for?

Answer 5

A narrow value range

Question 6

What kind of value range is a Class interval good for?

Answer 6

Used for wide value ranges

Question 7

Describe a Class Interval scale

Answer 7

• The width of the interval is the number of values the in the interval
• Should choose widths like 10-20 intervals
• Choose odd number interval width

Question 8

Why should a class interval have an odd numbered interval?

Answer 8

Allows the midpoint to be a whole number

Question 9

What is a midpoint?

Answer 9

The point halfway through the interval

Question 10

What limits are best to use for continuous variables?

Answer 10

Exact limits

Question 11

Describe exact limits

Answer 11

1/2 unit below and 1/2 unit above the class interval

Question 12

How would you calculate the midpoint when using exact limits?

Answer 12

Lower exact limit + 1/2 class interval width

Question 13

What are the axes for a frequency polygon and histograms?

Answer 13

X axis = mark axis with values corresponding to Class Interval midpoint
Y axis = frequency

Question 14

In a histogram would you put space between the bars for continuous data?

Answer 14

No

Question 15

Describe uniform/rectangular distribution shape

Answer 15

Evenly distributed throughout

Question 16

Describe skewed distribution shape

Answer 16

Lots of scores at one end and relatively few at other end

Can be positive or negative

Question 17

Of which end of the distribution would positively skewed data be?

Answer 17

Left

Question 18

Of which end of the distribution would negatively skewed data be?

Answer 18

Right

Question 19

Describe normal distribution

Answer 19

• Symmetric distribution

- Many scores in the middle, progressively fewer at either end