Minitab Confidence Intervals
Minitab
• At the top is the Session Window
• At the bottom is the Worksheet
• Enter the data into a column using cut-andpaste from excel
9.94
11.55
11.4
7.91
9.31
9.08
12.72
10.89
8.16
11.04
7.67
9.21
13.3
13.36
12.21
9.31
10.05
12.14
13.9
7.2
12.54
12.65
9.07
13.43
10.26
Summary Statistics and Plots
Stat ! basic stats ! display descriptive statistics !
enter x as the variable (type or click on x in the box
on the left) ! click “Options” or “Graphs” if desired
and complete the dialogues ! OK
In Options select the statistics you want minitab to
calculate, then click OK.
In Graphs select the plot you want minitab to make,
then click OK.
The statistics output will be displayed in the session window. A new window will open
to display the graph. The session window and graphs can be cut-and-pasted into word or
printed directly to paper (file ! print session window, print graph etc).
Descriptive Statistics: x
Variable
x
N
25
N*
0
Mean
10.732
Variable
x
Maximum
13.900
SE Mean
0.401
StDev
2.007
Minimum
7.200
Q1
9.145
Median
10.890
Q3
12.595
Histogram (with Normal Curve) of x
Histogram (with Normal Curve) of x
Mean
StDev
N
6
10.73
2.007
25
Frequency
5
4
3
2
1
0
6
8
10
12
14
x
Histogramof x
Assessing Normality Graphically
6
Graph ! histogram ! simple ! graph
variables: x ! OK
Frequency
5
4
3
2
1
0
7
8
9
10
11
x
12
13
14
Boxplot of x
14
Graph ! boxplot ! simple ! graph
variables: x ! OK
13
12
x
11
10
9
8
7
Probability Plot of x
Normal - 95% CI
Graph ! probability plot ! single ! graph
variables: x ! OK
99
Mean
StDev
N
AD
P-Value
95
90
Percent
80
70
60
50
40
30
20
10
5
1
5.0
7.5
10.0
12.5
x
Confidence Interval for a Mean
Stat ! basic stats ! 1-sample t ! enter x as the
variable (type or click on x in the box on the left) !
click “Options” or “Graphs” if desired and complete
the dialogues ! OK
In Options you specify 100(1-α) for the CI, then click
OK. If you omit this step, minitab will default to a
95% CI
15.0
17.5
10.73
2.007
25
0.394
0.348
Welcome to Minitab, press F1 for help.
One-Sample T: x
Variable
x
N
25
Mean
10.7320
StDev
2.0074
SE Mean
0.4015
95% CI
(9.9034, 11.5606)
Note: Minitab does not allow you to construct a CI for a mean unless you know σ.
Minitab, correctly, uses the t distribution for all CIs for a mean.
Confidence Interval for a Proportion
Stat ! basic stats ! 1-proportion ! enter x as the
variable (type or click on x in the box on the left) !
click “Options” if desired and complete the dialogues
! OK
In Options you specify 100(1-α) for the CI, then click
OK. If you omit this step, minitab will default to a
95% CI
Test and CI for One Proportion: x
Test of p = 0.5 vs p not = 0.5
Event = 1
Variable
x
X
16
N
50
Sample p
0.320000
99% CI
(0.164384, 0.510774)
Exact
P-Value
0.015
Statistical Tables
Calculate ! probability distributions ! chi-square
Inverse Cumulative Distribution Function
Chi-Square with 16 DF
P( X <= x )
0.025
x
6.90766
Inverse Cumulative Distribution Function
Chi-Square with 16 DF
P( X <= x )
0.975
x
28.8454