Here, we are required to estimate Q1, the median, and Q3 from the histogram and determine if the mean of this data set is smaller or larger than the median.
(a)
Q1 = 7
Q1 = 7median = 15
Q1 = 7median = 15Q3 = 40
(b). When data plotted on a bar chart as this, is heavily skewed to the left, the mean is very much larger than the median.
(a) To estimate first quartile, Q1, median (Q2) and third quartile, Q3.
1. The first quartile corresponds to 1/4 i.e 0.25 of the cumulative frequency distribution. It's in the first bar as the bar corresponds to 0.38 on the fraction of countries axis. Therefore, we can estimate Q1 = 5.
However, since 0.38 is slightly higher than 0.25, we can estimate Q1 to be slightly higher than 5.
And since the bar represents a range from 0 to 10
Therefore, Q1 = 7
2. Secondly, to estimate the median, the point where the 2nd quartile falls on the cumulative frequency distribution (i.e the 0.5 fraction).
Therefore, since the 1st bar has 0.38 fraction of the frequency, and the 2nd bar has 0.22 of the frequency. The total of both bars gives a cumulative frequency of 0.60.
Therefore, since the median falls around half way through the second bar, the median can be estimated as median = 15.
3. Lastly, Q3 falls around the 0.75 of the cumulative frequency distribution.
Since the third bar corresponds to 0.11 fraction of countries and the 4th bar corresponds to 0.07 fraction of countries.
Consequently, the cumulative frequency of the fraction of countries becomes 0.60 + 0.11 + 0.05.
Total then becomes 0.76.
The Q3 is therefore around the far end of the 4th bar and then can be estimated as Q3 = 40.
(b). When data plotted on a bar chart as this, is heavily skewed to the left, the mean is very much larger than the median.
By observing, the frequency of data from the far end. The cumulative frequency of the data from 80 to 120 falls around 5% so adds only a small impact on the mean, same for the cumulative frequency of the data from 80 to 60 and 60 to 40. Therefore, the mean is then way larger than the median.
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