Mark Scheme (Results) - Edexcel

1 Mark Scheme (Results). January 2018. Pearson Edexcel International Advanced Subsidiary Level In Statistics S1 (WST01). Paper 01. Edexcel and BTEC Qualifications Edexcel and BTEC qualifications are awarded by Pearson, the UK's largest awarding body. We provide a wide range of qualifications including academic, vocational, occupational and specific programmes for employers. For further information visit our qualifications websites at or Alternatively, you can get in touch with us using the details on our contact us page at Pearson: helping people progress, everywhere Pearson aspires to be the world's leading learning company.

2 Our aim is to help everyone progress in their lives through education. We believe in every kind of learning, for all kinds of people, wherever they are in the world. We've been involved in education for over 150 years, and by working across 70 countries, in 100 languages, we have built an international reputation for our commitment to high standards and raising achievement through innovation in education. Find out more about how we can help you and your students at: January 2018. Publications Code WST01_01_1801_MS. All the material in this publication is copyright Pearson Education Ltd 2018.

3 General Marking Guidance All candidates must receive the same treatment. Examiners must mark the first candidate in exactly the same way as they mark the last. Mark schemes should be applied positively. Candidates must be rewarded for what they have shown they can do rather than penalised for omissions. Examiners should mark according to the mark Scheme not according to their perception of where the grade boundaries may lie. There is no ceiling on achievement. All marks on the mark Scheme should be used appropriately. All the marks on the mark Scheme are designed to be awarded. Examiners should always award full marks if deserved, if the answer matches the mark Scheme .

4 Examiners should also be prepared to award zero marks if the candidate's response is not worthy of credit according to the mark Scheme . Where some judgement is required, mark schemes will provide the principles by which marks will be awarded and exemplification may be limited. When examiners are in doubt regarding the application of the mark Scheme to a candidate's response, the team leader must be consulted. Crossed out work should be marked UNLESS. the candidate has replaced it with an alternative response. PEARSON Edexcel IAL MATHEMATICS. General Instructions for Marking 1. The total number of marks for the paper is 75.

5 2. The Edexcel Mathematics mark schemes use the following types of marks : M marks : Method marks are awarded for knowing a method and attempting to apply it', unless otherwise indicated. A marks : Accuracy marks can only be awarded if the relevant method (M). marks have been earned. B marks are unconditional accuracy marks (independent of M marks ). marks should not be subdivided. 3. Abbreviations These are some of the traditional marking abbreviations that will appear in the mark schemes. bod benefit of doubt ft follow through the symbol will be used for correct ft cao correct answer only cso - correct solution only.

6 There must be no errors in this part of the question to obtain this mark isw ignore subsequent working awrt answers which round to SC: special case or equivalent (and appropriate). d or dep dependent indep independent dp decimal places sf significant figures The answer is printed on the paper or ag- answer given or d The second mark is dependent on gaining the first mark 4. All A marks are correct answer only' (cao.), unless shown, for example, as A1 ft to indicate that previous wrong working is to be followed through. After a misread however, the subsequent A marks affected are treated as A ft, but manifestly absurd answers should never be awarded A marks .

7 5. For misreading which does not alter the character of a question or materially simplify it, deduct two from any A or B marks gained, in that part of the question affected. 6. Ignore wrong working or incorrect statements following a correct answer. Question Scheme marks Number 1. (a) [61 15 ] 915 B1. (1). (b) 59610 58035 M1. [VarA ]= 77 2 [ VarB ] = 612. 10 15. = 32 = 148 A1 A1. (3). (c) Class B since its variance is larger B1ft (1). (d)(i) 770 "915" 10 15 M1 A1. MeanAB = = or 77 61 25 25 25. (ii) 59 610 58 035. VarAB = " "2 = awrt 163 M1 A1. 25. (4). (e)(i) No effect on the variance of class A since addition does not change variance B1.

8 (Var (X + b) = Var (X)). (ii) The mean will increase since the total score has increased B1. or mean of A increased but mean of B stayed the same (iii) The variance of the entire group will increase since the mean of class A is now B1. further away from the mean of class B (3). [12 marks ]. Notes (b) M1 for a correct method for variance for either class. Accept s2 and allow inside .. 1st A1 for 1 correct answer. NB sA2 or awrt and sB 2 or awrt 159. 2nd A1 for both correct. [ISW standard deviations following correct variances.]. (c) B1ft for Class B and it has a larger variance/standard deviation (do not allow spread).

9 If VarA > VarB then allow choice of A since variance is larger. Ft their values if > 0. (d)(i) M1 for a correct calculation for the mean (or weighted mean), ft their 915 from (a). A1 for for use of correct formula (no .. ) with total x = 117 645 and their 25xx . 2 S 4076. (ii) M1 25. A1 for awrt 163 [Don't ISW standard deviation]. (e)(i) B1 for no effect/does not change and correct supporting reason that mentions addition or subtraction doesn't affect or only affected by multiplication/division. Comment that x x doesn't change is fine. Just coding is not sufficient. (ii) B1 for stating the mean will increase and correct supporting reason that states or implies that total (of scores) has increased.

10 Allow new mean = 1715 25 (iii) B1 for increase and correct supporting reason that mentions A marks and B marks and that they are more spread out. Just saying: marks are more varied or only added 3 to one class is not sufficient NB Calc for (iii) gives new x2 = 64 320 and VarAB = but no mark Question Scheme marks Number 2. (a) B1. (1). (b) [ P(C D) 0 ] B1. (i) 1 B1. P(C D) P(C ) P( D) . 2. (ii) B1. P(C D). P(C | D)[ ] 0. P( D ) (3). (c)(i) P( F G ) P( F ) P(G ) P( F G ). 3 1 1. P(G ) P(G ) M1 M1. 8 6 6. 1. P(G ) A1. 4. (ii) 1 B1. P( F | G )[ P( F )] . 6. (4). [8 marks ]. Notes nd (a) If a 2 diagram is drawn then award B0 unless the incorrect diagram is crossed out (b) 1st B1 for writing or using P(C D) 0 anywhere in (b)(may be implied by correct P(C | D)).