Which is the best estimate for the speed of a boy going fast on a skateboard? 1000 mph, 1 mph, 100 mph, 10 mph

The force acting on a beam was measured under the same operating conditions and a sample of 5 data points was collected. this process was repeated by 3 observers. the pooled standard deviations of these 3 data sets was 1.21. determine the true mean force using all pooled data (with a 95% probability). the result should look like this: true mean = mean +/- margin of error