# Teachers page: Vital Statistics

Mathematics level 4 Statistics:

Collect and display time series data.

Report the distinctive features of data displays.

Background

The learning outcomes are:

• Define 'vital statistics'.
• Display information in a line graph and explain the reason for using this graph.
• Discuss one way a graph can be misleading.
• Interpret a population graph.

1. Vital Statistics are statistics on births, deaths, marriages and divorces.
• Currently (March 2010), the estimated population demographics for New Zealand are:
Women = 50.9%    Men = 49.1%
• From the 2006 Census, the ethnic populations were:
European = 77%     Maori = 15%     Asian = 7%    Pacific Peoples = 10% Middle Eastern/Latin American/African = 1%(The total isn't 100 percent because some identify with more than one group).

1. A line graph is best because it shows change over time. Whether you are graphing seconds, minutes, hours, days or years, a line graph will best show the changes.
2. Some key things to watch with line graphs:
• The numbers up the y-axis should start at zero and go up in regular intervals.
• The years along the bottom should be evenly spaced. (Students could use excel or another spreadsheet to do their graph.)
• When joining the dots to make the line, start at the first number and end at the last. DO NOT START OR FINISH AT ZERO as this gives a false impression of change.

Encourage students to notice growth patterns and relationships between their two chosen statistics. Eg the increase in arrivals coinciding with decrease in departures.

1. Females live longer than males!
2. Graph should look the same but with much longer bars.
3. The break in the graph exaggerates the differences in life expectancy. The students’ graphs should give a more realistic portrayal.
4. 4%.
5. 2 %.
6. 35–39 (or 30–44).
7. There is a dip in the age groups 20–24 and 25–29. There could be a number of reasons for these dips.
There may have been fewer people born in the 1970s due perhaps to a greater percentage women being in the paid work force or many Kiwis in their 20s going overseas.

Extension: Have students visit www.stats.govt.nz and click on Population clock this shows the estimated population of New Zealand today. If you watch long enough you will see it tick over.