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There are two groups of data. The average value of the first group is larger than that of the second group. Is the standard deviation of the first group larger than that of the second group? Must it be big?
No, it's not necessarily that the standard deviation is the square of the variance. Large standard deviation means large data fluctuation. So if the average value is large but the data fluctuation is small, the standard deviation will be small
Take any five apples from a pile and weigh them as follows: (unit: G) 125124121123127. Then the standard deviation of the sample is -
Why is the answer 2? Isn't the sample variance divided by n-1?
If the standard deviation and variance are different, first calculate the average, then subtract the square of the average from each data, add it up and divide it by the number of data, and finally square it. Under the root sign, 1 / 5 [125-124] ^ 2 + (124-124) ^ 2 + (121-124) ^ 2 + (124-124) ^ 2 + (127-124) ^ 2 = 2
From a pile of apples, the mass is 125124121123127, then the sample standard deviation is s=____ (g)
The largest 127 plus the smallest 121 divided by 2 equals 124
Excel calculates standard deviation (based on probability, not sample value)
The function STDev (range) of standard deviation of sample value is calculated by Excel
Now I want to ask you if you know the probability of each value, is there a formula to calculate its standard deviation or variance?
For example: known
Probability value
0.2 5
0.8 6
0.2 9
How to use Excel formula to calculate data mean, variance or standard deviation?
Please do not provide mathematical formula,
Your probability is more than one,
The mean value should be the sum of number * probability, then C8 = summation ((A2: A4) * (B2: B4))
Similarly, the standard deviation is the square of the difference between the value and the mean multiplied by the probability sum and then squared
C9=sqrt(sumproduct((A2:A4)*(B2:B4-C8)^2)
Assume that the cells to be written are C8 and C9
What determines the type of atom? What about elements?
The type of atom is determined by the number of protons and neutrons in the nucleus and the arrangement of electrons outside the nucleus
The type of element is determined by the number of protons in the nucleus
Why is f = ma in the physical formula a ≠ g in the car experiment of Newton's second law
The experiment in physics compulsory one of senior one: there is a fixed pulley on the edge of the board, and a weight (M weight is far less than m car) is hung under the fixed pulley. Then the other end of the rope is tied to a car, and the board is slightly raised to balance the friction. Why is the acceleration of the car and weight a ≠ the acceleration of the gravity g
This is an obvious problem
Because only the weight is pulled downward, and the gravity of the car on the slope is balanced by the slope
Only when the gravity of the weight and the car contribute to the acceleration, the acceleration is equal to the gravity acceleration G
What determines the kind of atom?
The type of atom is determined by the number of protons and neutrons
The type of element is determined only by the number of protons
What's the matter with the formula f-f = ma? Isn't Newton's second law f = ma?
F is external force
In f-f = ma, f-f is the external force on the body
What determines the type of atom?
Proton number (nuclear charge number)
The expression of Newton's second law
F = ma, f is the external force, M is the mass, a is the acceleration
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