The given scores corresponds to 10 randomly chosen fifth grade students.
145
139
126
122
125
130
096
110
118
118
a)
To make the stemplot, you can use the first two digits of each value for the stem and the last digit as the leaves:
First order the observations from least to greatest:
096, 110, 118, 118, 122, 125, 126, 130, 139, 145
Starting from the smaller value "09" determine the stem:
09|
10|
11|
12|
13|
14|
Then add the leaves to each corresponding stem, notice that there are no observations for "10", you have to put no values in that row, this means that there are no observations that correspond to it.
09| 6
10|
11| 0 8 8
12| 2 5 6
13| 0 9
14| 5
b)
An outlier is an observation that is significantly distant from the rest of the data set. They usually represent experimental errors (such as a measurement) or atypical observations.
Considering the 1st quartile (Q₁), the 3rd quartile (Q₃) and the interquartile range IQR, any value X is considered an outlier if:
X < Q₁ - 1.5 IQR
X > Q₃ + 1.5 IQR
The position of PosQ₁=n/4=10/4=2.5 → to determine the 1st quartile you have to identify the values in positions 2 and 3 and
Q₁= 114
Q₃=