Question

the mean of first 8 observation is 18 and last 8 observation is 20 .if the mean of all 15 observation is 19 .find the 8th observation ​

Answer 1

Answer:

19

Step-by-step explanation:

Mean = Sum of all observations/number of observations

mean of all 15 observations = 19

=> Sum of all 15 observations = 19 * 15 = 285.

Since number of observations is 15, 8th observation is in the middle.

Mean of first 8 observations = 18

=> Sum of first 8 observations = 8 * 18 = 144.

So, sum of last 7 observations = 285 - 144 = 141.

Mean of Last 8 observations = 20

=> Sum of last 8 observations = 8 * 20 = 160.

We have already found sum of last 7 observations as equal to 141.

So the 8th observation would be = 160 - 141 = 19.