Ch. 3: Data, Graphs, and Distributions

Question 1

Discrete

Answer 1

• Come in certain chunks. Shoe sizes can only be 5, 9 ½, 12, etc. The only possibilities are certain points on the number line. Every data point will be one of this limited set of choices, even if “limited” means a whole bunch of choices.
• Anything that you can count
• Exact number
• Ex: Number of people

Question 2

Continuous

Answer 2

• Can be anywhere in a given range, not just at certain points. There may be a maximum and/ or a minimum, but infinite possible outcomes.
• Anything that you can measure
• Infinite possibilities
• Ex: VO2 max can be 27.896

Question 3

Frequency distribution

Answer 3

Frequency of preferences table used to summarize qualitative data

Question 4

Relative Frequency distribution

Answer 4

We can write the same information as a relative frequency distribution. A “relative frequency” is just the frequency divided by the total number.
- Qualitative data can be summed in a bar, pie, or chart

Question 5

5 ways to summarize quantitative data

Answer 5

Frequency distribution chart
 Relative frequency distribution chart
 Dot plots
 Histogram
 Ogive

Question 6

Frequency table

Answer 6

To make a frequency table, we need groupings, or classes. Let’s go by chunks of 0.5 from zero to 3, and then just have a “more” category.

Question 7

Dot plot

Answer 7

Just listing the number of data points in each class gives us the frequency distribution. A “dot plot” is the same in a picture.
- Pretty straightforward, right? One point for each number in the data.

Question 8

Histogram

Answer 8

A histogram is an improved dot plot, using bars instead of dots. Unlike a bar chart, a histogram may or may not have separation between the bars.

Question 9

Symmetry

Answer 9

A histogram is said to be symmetric if, when we draw a vertical line down the center of the histogram, the two sides are identical in shape and size

Question 10

Skewness

Answer 10

A skewed histogram is one with a long tail extending to either the right (negatively) or the left (positively)

Question 11

Modality

Answer 11

A unimodal histogram is one with a single peak, while a bimodal histogram is one with two peaks

Question 12

Bell shape

Answer 12

A special type of histogram is one that is bell shaped

Question 13

Ogive

Answer 13

(pronounced “Oh-jive”) is a graph of a cumulative relative frequency distribution. (Here’s a video about ogives- just the first few minutes.)

Question 14

3 steps for an ogive

Answer 14

We create an ogive in three steps:

1) Calculate relative frequencies.
2) Calculate cumulative relative frequencies.
3) Graph the cumulative relative frequencies

Remember that relative frequencies are:
Relative Frequency = # of observations in a class/Total # of observations

Question 15

Cross-tabulation table

Answer 15

is used to describe the relationship between two variables. It lists the frequency of each combination of the values of the two variables.
Cross-tabs work for quantitative and qualitative variables.

Question 16

Scatterplot

Answer 16

A scatterplot works for quantitative variables only. You have seen these many times.

Question 17

=Countif

Answer 17

Used to count how many of one variable is in the data set.

Countif data used to create pie charts and bar charts