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Community Issues Data Investigation

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Community Issues Data Investigation

A local residents’ group is concerned about traffic near a busy crossing. Analyse the sample data below, assess how it was collected, and decide what conclusions the group can responsibly draw. Show working where useful. Counts are the number of vehicles passing the crossing in each 10-minute period.

Time period

Kauri Street

Harbour Road

8:00–8:10 am

8:10–8:20 am

8:20–8:30 am

8:30–8:40 am

8:40–8:50 am

8:50–9:00 am

Read the evidence

Use the six recorded counts for each location in the data table.

1.Calculate the total number of vehicles counted at Kauri Street and at Harbour Road. Which location had the greater total, and by how many vehicles?

2.Find the mean vehicle count per 10-minute period for each street. Give your answers to 1 decimal place.

3.Find the median count for each street. Show how you ordered the counts before choosing the middle values.

4.Calculate the range of vehicle counts for each street. What does comparing the ranges tell you about variation in these six time periods?

5.Which street appears busier in this sample? Use at least two pieces of numerical evidence to support your conclusion.

Check the investigation

A useful statistical conclusion depends on how the data was gathered, not just on calculations.

6.The counts were collected by one volunteer on one weekday, from 8:00 to 9:00 am. Identify two limitations that make it risky to claim that Harbour Road is always busier than Kauri Street.

7.Propose a fairer follow-up sampling plan to compare the two streets. State when observations should be made and how the plan would improve the evidence.

8.A residents’ group wants to survey people about traffic. Which sampling method is most likely to reduce bias?

Ask only people who attend a meeting about traffic concerns.
Ask a randomly selected mix of residents from both streets and nearby areas.
Ask the first ten people who walk past the crossing.
Post a survey online and use only the responses from people who choose to complete it.

9.Write one neutral survey question that could collect useful information about traffic near the crossing. Avoid wording that pushes people towards a particular answer.

10.Give two ethical steps the group should take when surveying residents about traffic. Include how it could show manaakitanga (care and respect).

11.The group’s draft headline says, “Harbour Road traffic is 25% worse.” Is this a fair conclusion from the data? Explain what “worse” could mean and give a more accurate statement supported by the sample.