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What is the point estimate of the sample standard deviation? A question mentioned in the senior three exam, as mentioned above, people who know it tell me, Sheila
Ten bulbs are randomly selected from a certain batch for life test, and their life (in hours) is as follows: 105011001280125010410301101012401300_____ The expected value is 1050 + 1100 + 1120 + + 1280 + 1250 +
Is the theoretical value of the sample standard deviation the same as the population standard deviation
It's not the same size
Because there are two definitions, used in different situations:
If it is a population, divide n by the root of the standard deviation formula,
If it is a sample, divide the root of the standard deviation formula by (n-1),
Because we are exposed to a large number of samples, it is generally used to divide (n-1) within the root sign
The average and standard deviation are known in Excel. I want to produce a set of 120 digit data
It is generated according to the normal distribution, but it must be a positive number, not an integer. For example, the average is 15, and the standard deviation is 1.2
Try to use the function of "planning solution"
The idea is to specify 120 cell ranges first
Then, the calculation formula of mean and standard deviation is defined according to the area of 120 numbers
Then start planning solution
Add two conditions:
Average formula cell = known average
Cell of standard deviation formula = known standard deviation
Variable cells are specified as a range of 120 cells
Then solve it
Never tried, hope it works, ha ha
The type of atom determines the ()
The type of atom determines the ()
A: Relative atomic mass B: number of protons and neutrons in nucleus
C: Outermost electron number d: nuclear charge number
D
The type of element is determined by the number of protons
The number of protons (nuclear charge) in an atom is the same as the number of electrons outside the nucleus
So choose D
What are p v n r t in the formula PV = NRT?
What?
P Pressure
V volume
The quantity of substance n
R molar gas constant 8.31kpa * DM3 / mol-1
T Kelvin temperature
A. The atomic number of a is x, and the types of elements in the period of a and B are m and N, respectively
A. The atomic number of a is X. the number of elements in the period of a and B is m and N, respectively
If a and B are of the same ILA family,
When B is in the last period of a, the atomic number of B is
When B is in the next period of a, the atomic number of B is
If a and B are of the same family IIIA,
When B is in the last period of a, the atomic number of B is
When B is in the next period of a, the atomic number of B is
i
The difference of atomic number between the adjacent elements of group Ⅰ A and Ⅱ A is in the order of 1-2 period difference 2, 2-3 period difference 8, 3-4 period difference 8, 4-5 period difference 18, 5-6 period difference 18, 6-7 period difference 32. These differences are actually the number of elements contained in the previous period of the adjacent period
What do R and t stand for? I know the others
In ideal gas state, PV = NRT,
It is mainly used for normal temperature gas with low temperature and pressure
The ideal gas state constant R = 8.314j/mol/k
The gas pressure is p, the volume is V, n is the amount of gas substance, t is the gas temperature
Why are there more kinds of atoms than elements
The types of elements can be seen from the periodic table. However, almost all elements have isotopes. Physically, there are also antiprotons (negatively charged), that is to say, antiprotons are at the negative end of the table. More and more antimatter are found, which is why atoms are more than elements
What does the chemical formula PV = NRT mean? What is the multiplication of PV?
The equation of state of ideal gas (also called ideal gas law and Clapeyron equation) is an equation of state describing the relationship among pressure, volume, mass and temperature of ideal gas in equilibrium. It is based on Boyle's law, Charlie's law, Gai lusack's law and other empirical laws. PV = NRT (Clapeyron equation [1]
Matter made of carbon atoms
There are three kinds of materials directly composed of carbon atoms: (), (), (). The properties of the same kind of atoms are different. The main reason is that the () of atoms are different when they are composed
(graphite) (diamond) (carbon)
(arrangement)
It should be about the same
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