A10-ml pipette delivers 9.99,10.01,9.97, and 10.8 ml in an experiment. calculate the mean value and the average deviation from the mean.

To find the mean of a number of numbers, First you add them up.
9.99 + 10.01 + 9.97 + 10.8 = 40.77
Then, you divide the result by how much numbers you have (in this case 4)
40.77 / 4 = 10.1925

So, the mean value is 10.1925.

The deviation is the difference between the number and the mean.
(number - mean = Average deviation)

So you get:
9.99 - mean = 9.99 - 10.1925 = -0.2025
10.01 - 10.1925 = -0.1825
9.97 - 10.1925 = -0.2225
10.8 - 10.1925 = 0.6075

Now to find the Average deviation, you do the same steps as finding the mean. Add them up, and divide by 4 (because there is 4 numbers)
P.S. Negative numbers become positive.

0.2025 + 0.1825 + 0.2225 +0.6075 = 1.215

1.215 / 4 = 0.30375

So, the Average Deviation is 0.30375

Hope this Helps :)