| Exam Board | OCR MEI |
|---|---|
| Module | AS Paper 2 (AS Paper 2) |
| Year | 2022 |
| Session | June |
| Marks | 6 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Linear regression |
| Type | Comment on reliability/validity of prediction |
| Difficulty | Moderate -0.3 This question tests interpretation of linear regression models and extrapolation validity rather than calculation. Parts (a) and (c) require reading comprehension of pre-release material, (b) involves simple substitution to compare predictions, and (d) asks about long-term behavior of a linear model. While it requires statistical thinking about model appropriateness, the mathematical demands are minimal—no derivation of regression equations or complex analysis is needed. This is slightly easier than average A-level questions due to its primarily interpretative nature. |
| Spec | 2.01c Sampling techniques: simple random, opportunity, etc |
| Answer | Marks | Guidance |
|---|---|---|
| No evidence to support this statement as information in LDS is for \(16-64\) year olds | B1 | Oe; This age group not in data set; Must refer to data set |
| Answer | Marks | Guidance |
|---|---|---|
| Model 1: 68.98% | \*B1 | Reverse calculations; Model 1: 2019 (2018.9) |
| Model 2: 73% | \*B1 | Model 2: 2018 (2018.3) |
| Model 1 gives the best approximation since 68.98 is closer to true value | DB1 | Model 1 sufficient or unambiguous indication |
| Answer | Marks | Guidance |
|---|---|---|
| Not appropriate since employment trends vary across the boroughs | B1 | Oe; Westminster employment trends differs to other boroughs; employment specific only to Westminster |
| Answer | Marks | Guidance |
|---|---|---|
| eg Employment rates will increase forever; or eg Employment rates will exceed 100% | B1 | Oe; not just increase; not exponential; Constant growth; Rise over time; Increase every year; No limit/maximum |
## Question 6(a):
No evidence to support this statement as information in LDS is for $16-64$ year olds | **B1** | Oe; This age group not in data set; Must refer to data set
## Question 6(b):
Model 1: 68.98% | **\*B1** | Reverse calculations; Model 1: 2019 (2018.9)
Model 2: 73% | **\*B1** | Model 2: 2018 (2018.3)
Model 1 gives the best approximation since 68.98 is closer to true value | **DB1** | Model 1 sufficient or unambiguous indication
## Question 6(c):
Not appropriate since employment trends vary across the boroughs | **B1** | Oe; Westminster employment trends differs to other boroughs; employment specific only to Westminster
## Question 6(d):
eg Employment rates will increase forever; or eg Employment rates will exceed 100% | **B1** | Oe; not just increase; not exponential; Constant growth; Rise over time; Increase every year; No limit/maximum
---6 The pre-release material contains information about employment rates in London boroughs. The graph shows employment rates for Westminster between 2006 and 2019.
\begin{figure}[h]
\begin{center}
\captionsetup{labelformat=empty}
\caption{Employment rate in Westminster}
\includegraphics[alt={},max width=\textwidth]{e0b502a8-c742-4d78-993c-8c0c7329ec9c-05_641_1465_406_242}
\end{center}
\end{figure}
A local politician stated that the diagram shows that more than $60 \%$ of seventy-year-olds were in employment throughout the period from 2006 to 2019.
\begin{enumerate}[label=(\alph*)]
\item Use your knowledge of the pre-release material to explain whether there is any evidence to support this statement.
In order to estimate the employment rate in 2020, two different models were proposed using the LINEST function in a spreadsheet.
Model 1 (using all the data from 2006 onwards)\\
$\mathrm { Y } = 0.549 \mathrm { x } - 1040$,
Model 2 (using data from 2017 onwards)\\
$\mathrm { Y } = 2.65 \mathrm { x } - 5280$,\\
where $Y =$ employment rate and $x =$ calendar year.
It was subsequently found that the employment rate in Westminster in 2020 was 68.4\%.
\item Determine which of the two models provided the better estimate for the employment rate in Westminster in 2020.
\item Use your knowledge of the pre-release material to explain whether it would be appropriate to use either model to estimate the employment rate in 2020 in other London boroughs.
\item What does model 2 predict for employment rates in Westminster in the long term?
\end{enumerate}
\hfill \mbox{\textit{OCR MEI AS Paper 2 2022 Q6 [6]}}