Example

Title: One Variable Data

Grade: 1300-a Lesson: S4-L1

Explanation: The best way to understand SAT-2 is by looking at some examples. Take turns and read each example for easy understanding.

Examples:

Dataset A consists of the heights of 58 buildings and has a mean of 26 meters.
Dataset B consists of the heights of 40 buildings and has a mean of 59 meters.
Dataset C consists of the heights of 98 buildings from datasets A and B.
What is the mean, in meters, of dataset C?

Step 1a

Data set A: 75 buildings
Data set B: 50 buildings
Data set C: 125 buildings (combined total of A and B)

Explanation: Here, we discuss A, B, and C buildings.

Step 1b

To find the mean of data set C, we essentially need to find the average height considering the contribution of each building from sets A and B.
Let \$"M"_"c"\$ be the mean height of data set C.
We can express \$"M"_"c"\$ as a weighted average of the means of A \$("M"_"a")\$ and B \$("M"_"b")\$, weighted by the number of buildings in each set \$("N"_"a")\$ and \$("N"_"b")\$:

\$"M"_"c" = ("N"_"a" times "M"_"a" + "N"_"b" times "M"_"b")/("N"_"a" + "N"_"b")\$

Explanation: To calculate the mean of data set C, we factor in the contribution of buildings from sets A and B, representing this mean as a weighted average of the means of sets A and B, where \$"N"_"a"\$ and \$"N"_"b"\$ are the number of buildings in each set.

Step 1c

Total height of C = Total height of A + Total height of B = 1508 meters + 2360 meters = 3868 meters

Total number of buildings in C = number of buildings in A + number of buildings in B = 58 + 40 = 98

\$("Mean height of C") = ("Total height of C")/("Total number of buildings in C")\$

\$(3868 "meters")/ 98 = 39.47 "meters"\$

Explanation: Therefore, the mean height of dataset C is 39.47 meters.


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