4.4 Common statistical indicators
4.4.1 Average annual population
Average annual population is the denominator of the incidence (mortality) rates.We often use the arithmetic mean of the population at the beginning of the year and the end of the year as the approximate value of the annual average population.The formula is:
If the population changes evenly, the mid-year population, population at 00:00, July 1, can substitute for average annual population.
4.4.2 Sex- and age-specific population
Sex- and age-specific population is the population categorized by sex and different age groups and it can be calculated by interpolation.Age specific population is grouped by age groups of 5 years as follows: 0 ～1 years old, 1 ～4 years old, 5 ～9 years old, 10 ～14 years old…75 ～79 years old, 80 ～84 years old and 85+ years old.
4.4.3 Incidence (mortality) rate
Incidence (mortality) rate, also known as crude incidence (mortality) rate, is a measure of the frequency of an event, such as a new case of cancer(cancer death) occurring in a population over a period of time.The incidence is usually expressed as one hundred thousand points, and two decimal digits are retained after integer.The formula is:
4.4.4 Sex- and age-specific incidence(mortality) rates
Sex and age are important factors influencing cancer incidence and mortality.Sex-and age-specific incidence (mortality) rates are important indicators in cancer statistics.The formula is:
4.4.5 Age-standardized rate or age-adjusted rate (ASR)
Standardization is necessary when comparing several populations with different age structures because age has such a powerful influence on cancer incidence rate and mortality rate.ASR is a summary measure of the rate that a population would have if it had a standard age structure.In this report, the population standards we used are Segi's population and the fifth Chinese national census of 2000 for the world and China, respectively.(Table 2-3)
表2-3 标准人口构成
年龄标化发病（死亡）率的计算（直接法）：
（1）计算年龄组发病（死亡）率。
（2）以各年龄组发病（死亡）率乘以相应的标准人口年龄构成百分比，得到相应的理论发病（死亡）率。
（3）将各年龄组的理论发病（死亡）率相加，即是年龄标化发病（死亡）率。
Calculating ASR incidence (mortality)rate (direct method):
（1） Calculating the incidence (mortality) rate in each specific age groups.
（2） Multiplying incidence (mortality) rate of each age group by the corresponding age group composition of standard population is the theoretical incidence (mortality) rate.(https://www.daowen.com)
（3）Adding up the theoretical incidence(mortality) rate in each age group is the agestandardized incidence (mortality) rate.
6.分类构成
各类癌症发病（死亡）构成百分比可以反映各类癌症对居民健康危害的情况。癌症发病（死亡）分类构成百分比的计算公式如下：
7.累积发病（死亡）率
累积发病（死亡）率是指某病在某一年龄阶段内按年龄（岁）的发病（死亡）率进行累积的总指标。累积发病（死亡）率消除了年龄构成不同的影响，故不需要标准化便可以与不同地区直接进行比较。癌症一般计算0 ~74 岁人群的累积发病（死亡）率。
8.截缩发病（死亡）率
通常对癌症是截取35 ~64 岁这一易发年龄段计算，其标准人口常用世界人口年龄构成。
因为癌症在35 岁以前发生频率较低的，而在65 岁以后其他疾病较多，干扰较大，所以采用35 ~64 岁这一阶段的截缩发病（死亡）率比较稳定（截缩率是标化率），便于进行比较。
4.4.6 Proportions
Proportional distribution indicates the sitespecific percentage level of incident cases (deaths)compared with total cases (deaths) recorded, reflecting the hazards of various cancer types to people health.The formula is:
4.6.7 Cumulative incidence (mortality) rate
A cumulative incidence or death rate indicates the probability of onset of cancer between birth and a specific age.The rate can be compared without age standardization because it is not affected by age structures.Cancer generally calculates cumulative rates at 0 ~74 years of age.
4.4.8 Truncated incidence (mortality) rate
Truncated rate is the calculation of rates over the truncated age of 35~64 years old, generally for cancer, using WHO world standard population.The data are presented as truncated rates mainly because the accuracy of age-specific rates in the elderly may be much less certain and the rates in the younger age groups may be rare.
