20 14 The registration for the senior high school entrance examination in Shenzhen has ended, and the physical education examination, English listening and speaking examination, senior high school entrance examination and so on are coming soon. Although next year's senior high school entrance examination scores will be calculated by the original scores, Shenzhen still adopts the standard score algorithm of 20 14 senior high school entrance examination. But many parents don't understand how the standard score is calculated. Today, Bian Xiao will talk about the calculation method of standard score and unveil its mystery.

First, the original score of a single subject is converted into standard score.

1, according to the principle of educational statistics, we set the standard score as z, that is, the standard deviation between the original score and the average score;

Expressed by the formula: Z=(X-A)/S

Among them: x is the original score of the child's dice; A is the average score of all candidates; S is the standard deviation of the test score.

2, standard deviation calculation formula:

Standard deviation s=√{( 1/n)[(x 1- mean) 2+(x2- mean) 2+(x3- mean) 2+...+(xn-mean) 2]}

Where: x 1, x2, x3, ... ……xn represents the score of each candidate (for example: x 1 represents the score of candidate A, x2 represents the score of candidate B, x3 represents the score of candidate C ...); N represents the number of candidates taking the exam; The average is the average score of all candidates divided by the number of candidates.

note:

①√ is called "root sign" in mathematics, which means to find the arithmetic square root of a number (that is, the square is equal to the positive number of this number).

② ""is a mathematical symbol used to represent three-level operation. When inputting mathematical formulas on the computer, this symbol is often used to represent the power because it is inconvenient to input the power. For example, the fifth power of 2 is usually expressed as 2 5; For example, 5 represents the square of 5, that is, the square of 5 (see power for the operation of power). For example, 4 3 = 4× 4× 4 = 64, which can be understood as the third power of 4.

3. Perform a linear transformation (T transformation) on the Z score.

Generally speaking, the converted standard score z has a decimal and a negative value, which is inconvenient in practical use, so it is necessary to carry out linear transformation (T transformation) on the score z: T=500+ 100Z.

The converted t is what we usually call the standard score. The average standard score is 500, that is, if a candidate's standard score is 500, then the student's score is in the middle among all the candidates who take the exam.

Of course, this is done on the premise of the normal distribution of the original score. If the distribution of the original score does not meet the requirements of normal distribution, it should be normalized first and then converted into standard score. The converted score is called normalized standard score, which is what we call standard score.

Second, the weighted total score. Single subject standard score x weight and then add up.

For example, a student's standard scores in a single subject are: Chinese 700, Mathematics 600, English 650, Science 700, Calendar 600, and Physical Education 700. According to this year's weight, the weighted total score is 3570.

Algorithm: the standard of a single subject is divided into x weights, and then added.

700 x 1+600 x 1+650 x 1+700 x 1.5+600 x 0.6+700 x 0.3 = 3570

3. Convert the weighted total score into the standard total score of six subjects.

Rank all candidates who take the exam with the weighted total score, and calculate the percentage of candidates who are lower than each score (called percentage score). Then, according to the calculated percentage grade of each synthetic total score, check the normal distribution table (the table below "Comparison table of standard score and percentage grade") to get the normalized standard normal score corresponding to each synthetic total score.

(1) For example, the intersection of 500 under column "T" and column "3" (standard score 503) is 5 1200002. This figure is expressed as the percentage of 5 1.2%, that is to say, 5 1.2% of all candidates are below 503.

② If the score is less than 500, look at it this way: for example, if a candidate's score is 453, then 1000-453=547, and the look-up ratio is 0.68080002, then1-0.68080002 = 0.319.

Please refer to the article: /article/6963.html for the comparison table of standard scores and 100-point scores.