Distribution Shapes
Symmetric distribution



1
The data values are evenly distributed on both sides
of the mean
Symmetrical shapes are not always unimodal
When the distribution is unimodal, the mean, median,
and mode are the same and are at the centre
In this assignment we examined hypothesis testing for the mean, now we examine hypothesis
testing for the standard deviation and proportions
1. For exercises 4, 8, and 15, on page 451452, provide the following:
a. State the hypotheses and identify the cl
4. A large university reports that the mean annual salary of parents for students in an undergraduate class
is $91,600. To see how this compares to the whole university, the president surveys 28 randomly selected
families and finds that their average annu
3. Find the 95% confidence interval for the variance and standard deviation of the ounces of coffee that a
machine dispenses in 12ounce cups. Assume the variable is normally distributed. The data is in the Excel
workbook.
Confidence interval for VARIANCE
GEOG 2420: Introductory Statistics
Assignment 7: Data
A. Draw the scatter plot for the variables
Data for Question 1
x
5
4
8
7
8
6
10
9
y
12
10
2
5
8
8
10
12
2
4
7
6
9
10
1. Highlight the data in both columns
2. Click on "Insert" tab
3. Click on "Scatter"
Confidence interval for the MEAN when standard
deviation for the population is not known (p. 369)
Is known?
Yes Use the z formula
No Use the t formula
T distribution is on p. 648 Table F
Exercise 13 p. 372
Given: = 15.9; n = 12; = 19.2; = 4.41; 95% confid
Discrete Variables
Variables that assume values that can be counted (e.g., number of children in a family, number of students in a classroom).
Continuous Variables
Variables that assume an infinite number of values in an interval between any two specific
192
193
206
192
198
94
70
83
94
99
Analysing the scatter plot
There are several relationships that can exist between the x values and the y values (pp. 9596)
Construct a pie graph in Excel
The colour of 2014 Honda Civics in a dealership lot
Colour
White
1. Convert from Fahrenheit to Celcius
F
134
109
116
105
115
106
121
104
117
114
C
(use =convert formula)
56.66667
42.77778
46.66667
40.55556
46.11111
41.11111
49.44444
40
47.22222
45.55556
2. Calculate the variance and the standard deviation for the popul