Unit 2: Univariate Data Analysis - Grade 9

Question 1

Mean

Answer 1

average
- add up numbers and divide by amount

Question 2

Median

Answer 2

• order data from least to greatest
• find middle observation (if there are two, find average of them)
• n+1/2

Question 3

Mode

Answer 3

most frequent observation

Question 4

If number of median is odd

Answer 4

location of median: n + 1/ 2
- n = number of observations

Question 5

Data can be

Answer 5

Qualitative: no numerical value
- ex: eye color, hair color, nationality, etc…
Quantitative: numerical value
- ex: height, weight, length, capacity, volume, etc…

Question 6

Quantitative data can be:

Answer 6

Discrete = can be counted (how many?)
- ex: number of cars on a highway
- has no overlapping boundary values and there are gaps between the class intervals. Both inequalities are ≤ , for example 35 ≤ x ≤ 40, 41 ≤ x ≤ 45
Continuous = can not be counted (measured)
- ex: weight, height, speed, etc…
- has overlapping boundary values and is written with continuous intervals, with one < sign and one ≤, for example, 35 < x ≤ 40, 40 < x ≤ 45

Question 7

Stem-and-leaf diagram

Answer 7

• the stem represents the category figure
• the leafs represent the final digit(s) of each point
• the key tells you how to read the values

Question 8

Remember to add a key

Answer 8

ex - key 3: 9 represents 39 surveys

Question 9

Stem-and-leaf diagram meaning

Answer 9

a visual representation of ordered raw data which then can be analyzed.

Question 10

Any set of data has

Answer 10

5 number/point summary
- minimum value
- Q1: lower quartile (first quartile)
- median (second quartile)
- Q3: upper quartile (third quartile)
- maximum value

Question 11

Lower quartile (Q1)

Answer 11

the median of the values less than Q2

Question 12

Interquartile range

Answer 12

Q3 - Q1

Question 13

Box and whisker diagram

Answer 13

Great for the 5 point summary
- each piece contains 25% of the data

Question 14

Outliers

Answer 14

a member of a data set which does not fit with the general pattern of the rest of the data.

Question 15

To determine if a data value is an outlier

Answer 15

1) find Q1 and Q3
2) find IQR = Q3-Q1
3) Q1 - 1.5(IQR), Q3 = 1.5(IQR)

the outlier will be the number either less than or more than these two numbers.

Question 16

Frequency tables

Answer 16

shows the distribution of observations based on the options in a variable
- consists of quantitive data table, frequency and cumulative frequency

Question 17

Class width

Answer 17

the difference between the maximum and the minimum possible values in a class interval.

Question 18

Range from a group frequency table

Answer 18

(upper bound of highest - biggest - class interval) - (lower bound of lowest - smallest - class interval)

Question 19

Modal class

Answer 19

is the class containing the most data. It has the highest frequency.

Question 20

Mean for class interval

Answer 20

To find the mean, use the midpoint of each class interval to represent the data values in that class interval.
- ex: (1.20 + 1.30)/ 2 =1.25

Question 21

Standard deviation

Answer 21

is the measure of the deviation of the data from the mean
- symbol: sigma σ

Question 22

Variance

Answer 22

average of the sum of squares of deviation (the spread between numbers in a data set).

Question 23

Cumulative frequency graph

Answer 23

use the cumulative frequency from the table to graph, find the Q1, Q2, and Q3.
- x axis quantitive data
- y axis cumulative frequency