Easy -1.8 This is a straightforward recall question asking for a basic description of simple random sampling methodology. It requires only knowledge of standard sampling procedures (random number tables/generator) with no calculation, problem-solving, or statistical reasoning beyond stating a textbook method.
Number all the houses sequentially, or use house numbers
B1
Any mention of using house numbers, or houses, or other numbering. (List can be implied). *Not* random numbering unless correct subsequent method
Select using random numbers
B1
Mention random numbers. *Not* "select numbers randomly". Must be random method. NB: Using \(263 \times\) calculator Rand # is biased: B0. But "Ran#(263)" is unbiased.
Ignore numbers \(> 263\)
B1
3
# Question 1:
| Answer/Working | Marks | Guidance |
|---|---|---|
| Number all the houses sequentially, or use house numbers | B1 | Any mention of using house numbers, or houses, or other numbering. (List can be implied). *Not* random numbering unless correct subsequent method |
| Select using random numbers | B1 | Mention random numbers. *Not* "select numbers randomly". Must be random method. NB: Using $263 \times$ calculator Rand # is biased: B0. But "Ran#(263)" is unbiased. |
| Ignore numbers $> 263$ | B1 | **3** | Deal with problem of $> 263$, *or* repeats. "Select 20 random numbers between 1 and 263": B1B0 [If this, need to mention repeats to get last B1] |
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1 In Fisher Avenue there are 263 houses, numbered 1 to 263. Explain how to obtain a random sample of 20 of these houses.
\hfill \mbox{\textit{OCR S2 2011 Q1 [3]}}