It can be concluded that a certain increase in overall mortality rates of the population of N from cancer was caused only by changes in the age structure of the population. After the application of standardization and elimination of the influence of changes in the age composition was found that over the past 10 years, the population of the city was less likely to die from cancer.
Necessary to stress once again that the choice of a particular method of standardization depends on how full the statistical material available. The direct method gives more reliable results, but if he is unable to use or not use the indirect method of standardization reverse: they are accurate enough for practical use. Standardization allows us to draw a firm conclusion about whether there is really a difference in the overall intensity ratios compared collectives or those differences depend only on the uneven structure of the populations being compared.
In the study of a phenomenon changes over time component of the time series.
Dynamic series is a set of homogeneous statistical measures showing the change of a phenomenon for a certain period of time.
The values that make up the dynamic range, called a number of levels.
Levels of time series can be represented by:
- Absolute values;
- Relative values (including performance-intensive, extensive, value);
- Averages. Time series are of two kinds:
- Torque dynamic range consists of quantities characterizing the phenomenon at a certain point (date). For example, each level can characterize the population, number of doctors, etc. at the end of any year.
- Interval time series consists of the quantities characterizing the phenomenon for a certain period of time (interval). For example, each level of this series can characterize mortality, fertility, morbidity, the average annual occupancy rate for a year.
The interval time series, consisting of interval values.
The dynamics of fertility in St. Petersburg (1000 inhabitants):
1990 – 10.8
1993 – 6.6
1992 – 7.6
Torque dynamic series consisting of the absolute values. Dynamics of average annual population of St. Petersburg (in thousands):
The dynamic range can be subjected to transformations that aim to determine the characteristics of the studied process and to achieve clarity in the characterization of a phenomenon.
To determine the trend of the phenomenon are calculated, the time series:
- Absolute growth;
- An indicator of visibility;
- An indicator of growth (decline);
- The rate of increase (decrease).
Absolute growth is the difference between the previous and subsequent levels. Measured in the same units, which represent a number of levels.
Figures clearly shows the relationship of each level of the series to one of them (most basic), taken as 100%.
Rate of growth (decline) shows the relationship of each level to the previous one, taken as 100%.
Rate of increase (decrease) indicates the ratio of the absolute increase (decrease) in each level to the previous level, taken as 100%.
If the rate of growth (decline) shows how many percent of the previous level of the subsequent level, the growth rate shows the percentage increase (decrease) the next level compared to the previous one. Therefore, the growth rate can be calculated by the following formula and:
growth rate = growth rate of 100%
Dynamic range and its indicators may be represented in a table (Table 5.4).