First, arrange all the data in the sample from small to large. If the sample size is odd, the middle data is the median. If the sample size is even, the average of the middle two data is the median.
Definition of histogram:
Histogram, also known as mass distribution chart, is a statistical report chart, which uses a series of vertical stripes or line segments with different heights to represent the data distribution. Generally, the horizontal axis represents data type and the vertical axis represents distribution.
Histogram is an accurate graphic representation of digital data distribution. This is an estimate of the probability distribution of continuous variables (quantitative variables), which was first put forward by karl pearson. This is a bar graph. ?
In order to build a histogram, the first step is to segment the range of values, that is, divide the whole range of values into a series of intervals, and then calculate how many values are in each interval. These values are usually designated as continuous, non-overlapping variable intervals. Spaces must be adjacent and usually (but not necessarily) equal in size.
Histograms can also be normalized to show "relative" frequencies. Then, it shows the proportion of each case belonging to several categories, and its height is equal to 1.
Common functions of histogram:
1, showing the quality fluctuation state;
2. Intuitively convey information about process quality status;
After studying the quality fluctuation, we can master the process and determine where to focus on quality improvement.
Basic introduction of median:
Median is a proper term in statistics, which means a value in a sample, population or probability distribution. It can divide a group of values into equal upper and lower parts.
For a finite set of numbers, we can sort all the observed values and find the middle one as the median. If there are even numbers of observations, the median is not unique, and the average of the two intermediate values is usually taken as the median.
At most, half of the values in a data set are less than the median, and at most, half of the values are greater than the median. If the number of values greater than and less than the median is less than half, there must be some values in the set equal to the median.