An investigator has missed a value while collecting data in an experiment. Denoting the missing value by x, the observations are: 10, 4, 11, 6, 17, 15, 9, 8, x. What should be the value of x, if he wants mean = median = mode for this data set?
Explanation
For the mean, mode, and median to be equal, the data distribution must be perfectly symmetric.
Step 1: Calculate the mean
The sum of the 9 observations is:
10+4+11+6+17+15+9+8+x=80+x
Mean=980+x
Step 2: Analyze the median and mode
For a set to have a mode, a value must repeat. Currently, all values are distinct. If we set x to one of the existing values, it becomes the mode.
Let's test the options to see which value satisfies Mean=Mode=Median:
If x=10:
Sorted data: 4,6,8,9,10,10,11,15,17
Mean=980+10=990=10
Mode=10
Median (the 5th value) =10
Since Mean=Mode=Median=10, this satisfies the condition.
Correct Option: (b) 10