Results are out! Find what you Get quick advice or join the chat
Hey! Sign in to get help with your study questionsNew here? Join for free to post

S2 - Finding a critical region

Announcements Posted on
Score your uni out of 10 and help thousands of students chose the right uni 21-09-2015
Applying to uni? Take our 60-second survey - you could bag an Amazon voucher. 19-09-2015
  1. Offline

    im just about there, but i always seem to be one off of what the answer should be. for example:

    The probability of Brand A lotion curing a particular skin complaint it 0.35. Brand B is said to improve the cure rate. Brand B was tested on 20 people, and 10 people were cured of the problem. Show Brand B isnt significant at 0.05, and how many people out of 20 would be needed to be cured so the results are significant to 0.05?
    This means

    H0: p=0.35
    H1: p>0.35


    P(X≥10) = 1-P(X≤9) = 1-0.8782 = 0.1218. >0.05 therefore not significant.

    P(X≥c) ≤ 0.05

    1-P(X≤c-1) ≤ 0.05

    P(X≤c-1) ≥ 0.95

    now from the table,
    P(X=10) = 0.9468
    P(X=11) = 0.9804

    therefore c-1=11 and c=12

    but...the answer says its 11, not 12. what have i done wrong?
  2. Online

    I can't find anything wrong with your working.
    Where was the question from?
    The only thing I can think of is that they might have rounded 0.9468 to 0.95, but it's very unlikely.
  3. Offline

    I can't see anything wrong with your working either. Where did you get this question from, is from the book or an exam paper?
  4. Offline

    nope, nothing wrong with your answer, think the book is wrong on this one, i hate it when this happens cuz then you keep thinking youve made the mistake and keep goin over an ovr tryin to find something that isnt there.
  5. Offline

    it was from my Heinemann S2 textbook. i seem to get them wrong in past papers by about 1 like i said, so i went back to my textbook and started doing lots of the same type of question.

    im gonna keep practicing them anyway, but its good news that i did it right and it is the answer that is wrong.


Submit reply


Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. By joining you agree to our Ts and Cs, privacy policy and site rules

  2. Slide to join now Processing…

Updated: June 4, 2007
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

Today on TSR

Desert Island Discs

What are you eight favourite songs?

Should the UK leave the European Union or remain a member?
Study resources
Quick reply
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.