Question

Here is a data set:

303	288	224	283
365	264	274	297
300	447	297	325
249	387	294	383
369	348	375	359
381	380	203	402
256	382	330	258

Construct a grouped frequency distribution table (GFDT) for this data set. You want 10 classes with a "nice" class width. A "nice" class width would be a multiple of 5 or 10. Your classes should be labeled using interval notation. Since the data appears to be discrete, use a closed-interval to label each class. Each class should contain its lower class limit, and the lower class limits should all be multiples of the class width.

(Note: interval notation for closed intervals will take the following form "[number,number]")

Data range	Frequency

Answer 1

There are 10 classes, with class width 25, a multiple of 5. The highest number in the data is 447 and lowest 203 so we take the nearest integers to them which are a multiple of 5, i.e. 450 and 200 respectively to construct the classes.

Classes are denoted using closed interval notations. For example, [200,225] means greater than or equal to 200 and less than or equal to 225. According to the problem, each class should contain its lower class limit, hence in [200,225] for example, we will count the value 200, and not 225 if there are any. We will count 225 in the following class [225,250].
Thus we get,

Data range	Frequency
[200,225]	2
[225,250]	1
[250,275]	4
[275,300]	5
[300,325]	2
[325,350]	3
[350,375]	3
[375,400]	6
[400,425]	1
[425,450]	1