收集数据需要我们对所观察的现象进行测量，包括定性测量和定量测量。即，我们用变量来量化地描述概念。
不同的变量能够被量化的程度有所不同，变量的测度等级按照这种被量化的程度可以分为以下四类1)：
命名测度(nominal scale)：也称名义测度等级，是最低的一种测度等级，由一系列具有不同名称的类型组成。命名测度对观察结果进行标定和分类，但数据没有大小之分。命名测度等级也可以用数字表示，不过这些数字仅可定性，并不反映定量信息，也不可比较，如样本代号和数字、编码等。命名数据不支持四则运算，仅支持等于或不等于、是或不是。
Nominal scale,also known as the nominal measurement grade, it is the lowest measurement grade and consists of a series of types with different names. Named measures calibrate and classify observations, but there is no difference in size of the data. Named measure grades can also be expressed as numbers, but these numbers are only qualitative and do not reflect quantitative information, and are not comparable,such as sample codes and numbers, codes, etc.Nominal data does not support any form of arithmetic computation,and the only kind of mathematical opration it supports is equal to or not equal to, yes or no.
顺序测度(ordinal scale)：量化水平高于命名测度等级，由一系列按顺序排列的范畴组成。将观察所得结果按其大小或数量排定秩次(rank)，可以提供不同个体之间的顺序差异。顺序数据点之间可进行大小比较，但其本质依旧是定性而非定量的，因此不支持四则运算，也无法体现数据点之间差异的大小及程度。
Ordinal scale has a higher quantification level than nominal scale, and consists of a series of sequential categories. Ranking the observations by their size or number can provide sequential differences between different individuals. Sequential data points can be compared in size, but they are still qualitative rather than quantitative, so it does not support any form of arithmetic computation as well, and the magnitude and extent of the differences between data points cannot be reflected.
等距测度(interval scale)：也称间距测度等级，沿数字刻度测量，拥有更高的量化水平。相较于顺序测度，规定每两个相邻范畴之间距离相等。一般是采用一定单位的实际测量值，可以用加减运算得到数值之间的差或和，反映大小差距。但缺少物理意义上的绝对零点，因此乘除运算没有意义。一些心理量表，如里科特5点等级量表和是/否的两点量表就是常见的等距量表。
Interval scale，also known as the spacing measurement grade,has a higher quantification level than ordinal scale. It is measured along a numerical scale.In contrast to the sequential measure, the distance between every two adjacent categories is equal. Generally used the actual measured value in a certain unit, and the difference or sum between the values can be obtained by addition and subtraction operations to reflect the size difference. But the true 0 point in the physical sense is missing, so multiplication and division is meaningless. Some psychological scales, such as the Ricott 5-point scale and the yes/no two-point scale, are common isometric scales.
比例测度(ratio scale)：是最高的测度等级，除等距测度的特征外，还拥有绝对零点,可以表示差异的比率。可以进行乘除运算，反映数量间的比例关系。
Ratio scale is the highest measurement grade.In addition to the characteristics of equidistant measurements, it also has an true 0 point,and the ratios of differences can be expressed. Multiplication and division operations can be performed to reflect the proportional relationship between quantities.
各种测量类型的局限性直接关系到统计分析方法的选取，因此在开始收集实验数据之前，应格外注意。
The limitations of the various measurement types are directly related to the selection of statistical analysis methods, and therefore extra care should be taken before starting to collect experimental data.