Statistics
posted by ReeSha .
The Hill of Tara in Ireland is a place of great archaeological importance. This region has been occupied by people for more than 4,000 years. Geomagnetic surveys detect subsurface anomalies in the earth's magnetic field. These surveys have led to many significant archaeological discoveries. After collecting data, the next step is to begin a statistical study. The following data measure magnetic susceptibility (centimetergramsecond 10−6) on two of the main grids of the Hill of Tara.
Grid E: x variable
14.51 14.88 35.23 17.10 24.87 6.74 13.77
21.17 11.18 13.77 35.60 28.20 11.55 7.85
Grid H: y variable
16.11 40.55 23.63 51.83 20.81 17.52 45.25
46.19 12.35 10.00 46.66 26.92 13.29 24.10
(a) Compute Óx, Óx2, Óy, Óy2. (Round your answers to two decimal places.)
Óx =__
Óx2 = ___
Óy = ___
Óy2 = ___
(b) Use the results of part (a) to compute the sample mean, variance, and standard deviation for x and for y. (Round your answers to two decimal places.)
Grid E: x =
s2 =
s =
Grid H: y =
s2 =
s =
(c) Compute a 75% Chebyshev interval around the mean for x values and also for y values. (Round your answers to two decimal places.)
Grid E:
11 to 12
Grid H:
13 to 14

I cannot answer all your questions. I do not know what the "apple" symbol signifies.
b. For both x and y, add the scores and divide by n to find the mean. Subtract the mean from each score, and square each one. The sum of these squared differences = variance. The variance = s^2 = s squared, so standard deviation = square root of variance. 
Gjbdd