2. Key Concepts
2. Deciles for grouped data
1. Quartiles for grouped data
3. Percentile for grouped data
4. Percentile rank
3. The quartiles are
the score points
which divide a
distribution into
four equal parts.
1. Quartiles
for grouped
data
4. The steps in computing the median are similar to that
of Q1 and Q3. In finding the median, determine the
median class. In the same manner, Qı and Q3 class
must be determined first before computing the value
of Q1 and Q3. The Q1 class is the class interval where
the (N/4)th score is contained, while the class interval
that contains the (3N/4)th score is the Q3 class.
6. Calculate the Q1, Q2, and Q3 of the Mathematics test
scores of 50 students.
Example
7.
8. The lower class limit of a class is the smallest data
value that can go into the class. (data on the left)
The upper class limit of a class is the largest data
value that can go into the class. (data on the right)
The class interval (i) is the difference of upper limit
and lower limit plus one. For instance, (25-21)+1=4+1=5.
9.
10.
11.
12. Deciles are those values that
divide the total frequency into 10
equal parts.The kth decile denoted
by Dk is computed as follows:
2. Deciles for grouped
data
22. 4. PERCENTILE
RANK
Percentile ranks are particularly useful in relating individual
scores to their positions in the entire group. A percentile
rank is typically defined as the proportion of scores in a
distribution that a specific score is greater than or equal to.
For instance, if you received a score of 95 on a
mathematics test and this score was greater than or equal
to the scores of 88% of the students taking the test, then
your percentile rank would be 88.
