OCR MEI Further Statistics A AS 2020 November — Question 6 12 marks

Exam BoardOCR MEI
ModuleFurther Statistics A AS (Further Statistics A AS)
Year2020
SessionNovember
Marks12
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicChi-squared goodness of fit
TypeSpreadsheet-based chi-squared test
DifficultyStandard +0.3 This is a straightforward chi-squared test question requiring students to fill in missing values in a partially completed spreadsheet using standard formulas (expected frequencies = row total × column total / grand total, and contributions = (O-E)²/E). The calculations are routine and the context is clearly structured, making it slightly easier than average for A-level Further Statistics.
Spec5.06a Chi-squared: contingency tables

6 A researcher is investigating whether there is any relationship between whether a cyclist wears a helmet and the distance, \(x \mathrm {~m}\), the cyclist is from the kerb (the edge of the road). Data are collected at a particular location for a random sample of 250 cyclists. The researcher carries out a chi-squared test. Fig. 6 is a screenshot showing part of a spreadsheet used to analyse the data. Some values in the spreadsheet have been deliberately omitted. \begin{table}[h]
ABCDEFG
1\multirow{2}{*}{}Observed frequency
2\(\boldsymbol { x } \boldsymbol { \leq } \mathbf { 0 . 3 }\)\(0.3 < x \leq 0.5\)\(0.5 < x \leq 0.8\)x > 0.8Totals
3\multirow[t]{2}{*}{Wears helmet}Yes26272346122
4No45312131128
5\multirow{2}{*}{}Totals71584477250
6
7Expected frequency
8\(\boldsymbol { x } \boldsymbol { \leq } \mathbf { 0 . 3 }\)\(0.3 < x \leq 0.5\)\(0.5 < x \leq 0.8\)\(\boldsymbol { x } \boldsymbol { > } \mathbf { 0 . 8 }\)
9\multirow[t]{2}{*}{Wears helmet}Yes34.648037.5760
10No36.352039.4240
11
12\multirow{2}{*}{}Contribution to the test statistic
13\(\boldsymbol { x } \boldsymbol { \leq } \mathbf { 0 . 3 }\)\(0.3 < x \leq 0.5\)\(0.5 < x \leq 0.8\)\(\boldsymbol { x } \boldsymbol { > } \mathbf { 0 . 8 }\)
14\multirow[t]{2}{*}{Wears helmet}Yes2.15850.06010.10871.8885
15No2.05730.05731.8000
16
\captionsetup{labelformat=empty} \caption{Fig. 6}
\end{table}
  1. Showing your calculations, find the missing values in each of the following cells.
    Carry out a hypothesis test at the \(10 \%\) significance level to investigate whether there is any association between helmet wearing and distance from the kerb.
  2. Discuss briefly what the data suggest about helmet wearing for different distances from the kerb.

Question 6:
AnswerMarks Guidance
6(a) E10: = 22.5280
44×128
E15:
250
2
(21−22.5280)
AnswerMarks
= 0.1036B1
M1
A1
AnswerMarks
[3]1.1a
1.1
AnswerMarks Guidance
1.1FT their E10
6(b) 22.5280
H : No association between helmet wearing and
0
distance from curb
H : Some association between helmet wearing and
1
distance from curb
Degrees of freedom = 3
Critical value = 6.251
Test statistic = 2.1585 + 0.0601 + ... + 1.8000 = 8.234
8.234 > 6.251 so reject H
0
There is sufficient evidence to suggest that there is
association between helmet wearing and distance from
AnswerMarks
curbB1
B1
B1
B1
M1
A1
AnswerMarks
[6]3.3
3.4
1.1
1.1
2.2b
AnswerMarks
3.5aNo further marks if incorrect cv
used
M1 for comparison of their ‘8.234’
(using their answer from (a)) with 6.251
leading to a conclusion
A1 for non-assertive conclusion in
context. FT their ‘8.234’
AnswerMarks Guidance
6(c) For distances of 0.3 or below the contributions of
2.1585 and 2.0573 suggest that more do not wear
helmets and fewer do than would be expected.
For distances greater than 0.8 the contributions of
1.8885 and 1.8000 suggest that more do wear helmets
and fewer do not than would be expected.
For distances between 0.3 and 0.8 things are as
expected if there were no association.
AnswerMarks
.E1
E1
E1
AnswerMarks
[3]2.3
3.5a
AnswerMarks
3.5aSC1 if contributions not mentioned but
comments are otherwise correct for
both ‘distances of 0.3 and below’ and
‘distances greater than 0.8’.
PPMMTT
OCR (Oxford Cambridge and RSA Examinations)
The Triangle Building
Shaftesbury Road
Cambridge
CB2 8EA
OCR Customer Contact Centre
Education and Learning
Telephone: 01223 553998
Facsimile: 01223 552627
Email: general.qualifications@ocr.org.uk
www.ocr.org.uk
For staff training purposes and as part of our quality assurance programme your call may be
recorded or monitored
Question 6:
6 | (a) | E10: = 22.5280
44×128
E15:
250
2
(21−22.5280)
= 0.1036 | B1
M1
A1
[3] | 1.1a
1.1
1.1 | FT their E10
6 | (b) | 22.5280
H : No association between helmet wearing and
0
distance from curb
H : Some association between helmet wearing and
1
distance from curb
Degrees of freedom = 3
Critical value = 6.251
Test statistic = 2.1585 + 0.0601 + ... + 1.8000 = 8.234
8.234 > 6.251 so reject H
0
There is sufficient evidence to suggest that there is
association between helmet wearing and distance from
curb | B1
B1
B1
B1
M1
A1
[6] | 3.3
3.4
1.1
1.1
2.2b
3.5a | No further marks if incorrect cv
used
M1 for comparison of their ‘8.234’
(using their answer from (a)) with 6.251
leading to a conclusion
A1 for non-assertive conclusion in
context. FT their ‘8.234’
6 | (c) | For distances of 0.3 or below the contributions of
2.1585 and 2.0573 suggest that more do not wear
helmets and fewer do than would be expected.
For distances greater than 0.8 the contributions of
1.8885 and 1.8000 suggest that more do wear helmets
and fewer do not than would be expected.
For distances between 0.3 and 0.8 things are as
expected if there were no association.
. | E1
E1
E1
[3] | 2.3
3.5a
3.5a | SC1 if contributions not mentioned but
comments are otherwise correct for
both ‘distances of 0.3 and below’ and
‘distances greater than 0.8’.
PPMMTT
OCR (Oxford Cambridge and RSA Examinations)
The Triangle Building
Shaftesbury Road
Cambridge
CB2 8EA
OCR Customer Contact Centre
Education and Learning
Telephone: 01223 553998
Facsimile: 01223 552627
Email: general.qualifications@ocr.org.uk
www.ocr.org.uk
For staff training purposes and as part of our quality assurance programme your call may be
recorded or monitored
6 A researcher is investigating whether there is any relationship between whether a cyclist wears a helmet and the distance, $x \mathrm {~m}$, the cyclist is from the kerb (the edge of the road). Data are collected at a particular location for a random sample of 250 cyclists.

The researcher carries out a chi-squared test. Fig. 6 is a screenshot showing part of a spreadsheet used to analyse the data. Some values in the spreadsheet have been deliberately omitted.

\begin{table}[h]
\begin{center}
\begin{tabular}{|l|l|l|l|l|l|l|l|}
\hline
 & A & B & C & D & E & F & G \\
\hline
1 & \multicolumn{2}{|c|}{\multirow{2}{*}{}} & \multicolumn{5}{|c|}{Observed frequency} \\
\hline
2 &  &  & $\boldsymbol { x } \boldsymbol { \leq } \mathbf { 0 . 3 }$ & $0.3 < x \leq 0.5$ & $0.5 < x \leq 0.8$ & x > 0.8 & Totals \\
\hline
3 & \multirow[t]{2}{*}{Wears helmet} & Yes & 26 & 27 & 23 & 46 & 122 \\
\hline
4 &  & No & 45 & 31 & 21 & 31 & 128 \\
\hline
5 & \multirow{2}{*}{} & Totals & 71 & 58 & 44 & 77 & 250 \\
\hline
6 &  &  &  &  &  &  &  \\
\hline
7 & \multicolumn{2}{|c|}{} & \multicolumn{4}{|c|}{Expected frequency} &  \\
\hline
8 &  &  & $\boldsymbol { x } \boldsymbol { \leq } \mathbf { 0 . 3 }$ & $0.3 < x \leq 0.5$ & $0.5 < x \leq 0.8$ & $\boldsymbol { x } \boldsymbol { > } \mathbf { 0 . 8 }$ &  \\
\hline
9 & \multirow[t]{2}{*}{Wears helmet} & Yes & 34.6480 &  &  & 37.5760 &  \\
\hline
10 &  & No & 36.3520 &  &  & 39.4240 &  \\
\hline
11 & \multicolumn{2}{|c|}{} & \multicolumn{4}{|c|}{} &  \\
\hline
12 & \multirow{2}{*}{} &  & \multicolumn{4}{|c|}{Contribution to the test statistic} &  \\
\hline
13 &  &  & $\boldsymbol { x } \boldsymbol { \leq } \mathbf { 0 . 3 }$ & $0.3 < x \leq 0.5$ & $0.5 < x \leq 0.8$ & $\boldsymbol { x } \boldsymbol { > } \mathbf { 0 . 8 }$ &  \\
\hline
14 & \multirow[t]{2}{*}{Wears helmet} & Yes & 2.1585 & 0.0601 & 0.1087 & 1.8885 &  \\
\hline
15 &  & No & 2.0573 & 0.0573 &  & 1.8000 &  \\
\hline
16 & \multicolumn{7}{|c|}{} \\
\hline
\end{tabular}
\captionsetup{labelformat=empty}
\caption{Fig. 6}
\end{center}
\end{table}
\begin{enumerate}[label=(\alph*)]
\item Showing your calculations, find the missing values in each of the following cells.

\begin{itemize}
  \item E10
  \item E15
\item In this question you must show detailed reasoning.
\end{itemize}

Carry out a hypothesis test at the $10 \%$ significance level to investigate whether there is any association between helmet wearing and distance from the kerb.
\item Discuss briefly what the data suggest about helmet wearing for different distances from the kerb.
\end{enumerate}

\hfill \mbox{\textit{OCR MEI Further Statistics A AS 2020 Q6 [12]}}