While skateboarding at 19 km/h, alana throws a tennis ball at 11 km/h to her friend oliver. if alana is the reference frame, the speed of the tennis ball is km/h.

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