Noise levels at 4 volcanoes were measured in decibels yielding the following data: 153,156,168,138 Construct the 99% confidence interval for the mean noise level at such locations. Assume the population is approximately normal. Step 1 of 4 : Calculate the sample mean for the given sample data. Round your answer to one decimal place.

153.8 dB

Step-by-step explanation:

The mean required in the firat step is calculated by dividing the sum of individual records by their frequency

Where n is frequency

In this case, since we are provided with four different records, their their sum will be given by

Sum x= 153+156+168+138=615 dB

Therefore, the mean will be

Rounding off to 1 decimal point, then the mean is approximately 153.8 dB

the correct option is 2.

step-by-step explanation:

according to the given information triangle abc is a right angle triangle with right angle at a. segment ab is 5 and segment ac is 7. point d is on segment bc and angles adb and adc are right angles.

it is given that triangles abd, cad, and cba are similar.

two triangles are similar if their corresponding sides are proportional.

in triangle cba, using pythagoras theorem

                      )

triangle abd and cba are similar,

                            (2)

triangle cad and cba are similar,

                      )

using (1), (2) and (3), we get

hence proved.

therefore option 2 is correct.

5: 20

step-by-step explanation: