STAT 245 Lecture Notes - Lecture 2: Decimal Mark, Box Plot, Interquartile Range
STAT 245 – Exercises #2
Solutions
Q1. The following data will be used in this exercise:
3.1 4.9 2.8 3.6 2.5 4.5 3.5 3.7 4.1 4.9
2.9 2.1 3.5 4.0 3.7 2.7 4.0 4.4 3.7 4.2
3.8 6.2 2.5 2.9 2.8 5.1 1.8 5.6 2.2 3.4
2.5 3.6 5.1 4.8 1.6 3.6 6.1 4.7 3.9 3.9
4.3 5.7 3.7 4.6 4.0 5.6 4.9 4.2 3.1 3.9
1. How many observations are there in the above data set?
Answer: 50 observations
2. Construct a dotplot from the above data set.
Follow the example in the section on Dotplots in Lecture 2.
Data
6.35.64.94.23.52.82.1
Dotplot of Data
3. Construct a stem-and-leaf plot from the above data set using the numbers before the decimal
point as stems and the numbers after the decimal point as leaves.
Decide which value should be your first stem and which value should be your last stem. Follow
the examples in Lecture 2 as a guide on how to construct a stem-and-leaf plot.
Stem
Leaves
1
6 8
2
1 2 5 5 5 7 8 8 9 9
3
1 1 4 5 5 6 6 6 7 7 7 7 8 9 9 9
4
0 0 0 1 2 2 3 4 5 6 7 8 9 9 9
5
1 1 6 6 7
6
1 2
4. Construct a distribution table for the above data using the classes 1.0 to <2.0, 2.0 to <3.0, …, 6.0
to <7.0. Your table should show the tally, the frequency, the relative frequency and the
percentage for all the classes. What is the class width used in this table?
Class
Tally
Frequency
Relative
Frequency
Percent
1.0 to <2.0
//
2
0.04
4
2.0 to <3.0
///// /////
10
0.2
20
3.0 to <4.0
///// ///// ///// /
16
0.32
32
4.0 to <5.0
///// ///// /////
15
0.3
30
5.0 to <6.0
/////
5
0.1
10
6.0 to <7.0
//
2
0.04
4
Total
50
1
100
