A student (Lisa) measures the background radiation due to energetic particles in the Dunn laboratory with...

A student (Lisa) measures the background radiation due to energetic particles in the Dunn laboratory with a Geiger counter. She samples the radiation rate by recording the number of events in twelve, consecutive, one-minute intervals. Her count record is as follows: 14, 11, 20, 15, 24, 12, 21, 11, 13, 21, 12, 19

A) What is the average background count rate (in cpm)? Correct, computer gets: 16.1

B)What is the standard deviation of this count rate? Answer: Last Answer: 4.42 Incorrect, tries 4/10.

C)If the radiation events obey Poisson statistics, what should Lisa expect for the standard deviation if she counted for 1500 intervals?

D)If a source of gamma radiation is at hand that is known to have an average activity of 80 cpm, alone, what should Lisa expect to measure for the average count rate when measuring this source's activity in the laboratory? Correct, computer gets: 96.1

E)The Geiger counter has a cylindrical detecting volume of length 3.4 cm and diameter 1.4 cm. Lisa estimates the number of events that her body would detect, for her measured background rate, by regarding its volume as a collection of many such tubes. She treats her volume as a box of height 135 cm, width 37 cm, and depth 20 cm. How many external radiation events does it register per minute?

I need help with B, D, E