Which element is loacted in group 17 period 6

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

Need this now! do pilots live long

This is for my 8th grade science class, i really don’t understand. can someone me? , lol.