Year 12s: what will be the first way you research your future options? >>

S2 MEI OCR 10th June 2014 Official Thread

Scroll to see replies

Thank you in this case I have to find the values of and and b in P(a<Y<b)=0.95 is this a two tailed test and how would you tell?

The alternative hypotheses determines whether the test is two tailed or not. If the mean or rho (in the alternative hypotheses) doesn't equal 0 then the test is 2 tailed. If the mean or rho are either bigger or smaller than 0 then the test is single tailed.

Posted from TSR Mobile

Reply 41

visualcocaine

Help please guys :confused:

- Definition of a significance level?
- Advantages and disadvantages of using a 1% significance level rather than a 5 % significance level.

Reply 42

dianaantemir

Original post by visualcocaine

Help please guys :confused:

- Definition of a significance level?
- Advantages and disadvantages of using a 1% significance level rather than a 5 % significance level.

The significance level is the probability of rejecting the null hypothesis in a statistical test even when it's in fact, true

And I don't really know the answer for the second question myself haha sorry

Posted from TSR Mobile

Reply 43

sasunerd

Original post by visualcocaine

Help please guys :confused:

- Definition of a significance level?
- Advantages and disadvantages of using a 1% significance level rather than a 5 % significance level.

Using 1% means it's less likely to reject the null hypothesis, disadvantage is that it's more likely to accept the alternative.

Reply 44

sg1029

Original post by visualcocaine

Help please guys :confused:

- Definition of a significance level?
- Advantages and disadvantages of using a 1% significance level rather than a 5 % significance level.

adv: less likely to reject the null hypothesis when it is true

disadv: more likely to accept the null hypothesis when it is false

Reply 45

visualcocaine

Original post by dianaantemir

Haha its cool, thank you though! :smile:

Reply 46

sasunerd

Oh whoooops, sg's got it. :biggrin:

Reply 47

visualcocaine

Original post by sasunerd

Using 1% means it's less likely to reject the null hypothesis, disadvantage is that it's more likely to accept the alternative.

Thank youuuu! :smile:

Reply 48

visualcocaine

Original post by sg1029

adv: less likely to reject the null hypothesis when it is true

disadv: more likely to accept the null hypothesis when it is false

Thank you! :smile:

Reply 49

visualcocaine

Why is no one really stressed about this exam? It's actually really easy to make silly mistakes on this paper :mad:

Reply 50

Hoosierette

Original post by visualcocaine

Why is no one really stressed about this exam? It's actually really easy to make silly mistakes on this paper :mad:

I am extremely stressed because I always make silly mistakes and I don't even understand 1/2 of it.

Reply 51

visualcocaine

Original post by Hoosierette

I am extremely stressed because I always make silly mistakes and I don't even understand 1/2 of it.

Ahh i understand but it's those little errors like getting a continuity correction wrong e.g 49.5 instead of 50.5 grrrrrr :angry:

Those little mistakes can bring me down by so much because they just accumulate!

Reply 52

dianaantemir

Original post by visualcocaine

Ahh i understand but it's those little errors like getting a continuity correction wrong e.g 49.5 instead of 50.5 grrrrrr :angry:

Those little mistakes can bring me down by so much because they just accumulate!

I am very stressed about this exam I want to get an A, this has helped me remember how to do continuity corrections ImageUploadedByStudent Room1402338177.054621.jpg

ImageUploadedByStudent Room1402338177.054621.jpg

Posted from TSR Mobile

Reply 53

visualcocaine

Original post by dianaantemir

I am very stressed about this exam I want to get an A, this has helped me remember how to do continuity corrections ImageUploadedByStudent Room1402338177.054621.jpg

Posted from TSR Mobile

aw thanks, that's actually helpful :smile:

Reply 54

Felt tip

sometimes the probabilities such as 0.1 are positive when working out what k is...why?

Reply 55

Felt tip

how would you do qn 3 part 2 and 3 http://www.mei.org.uk/files/papers/s209jn_7sg7.pdf

Reply 56

username1186351

Original post by Felt tip

sometimes the probabilities such as 0.1 are positive when working out what k is...why?

When k is above the mean, the inverse normal distribution value is a positive value, if it is below the mean then it is a negative value.

Reply 57

sasunerd

Original post by Tinglay

When k is above the mean, the inverse normal distribution value is a positive value, if it is below the mean then it is a negative value.

But sometimes you don't know what the mean is?

Reply 58

Jimmy_Whistles

For part 2 you'd set up simultaneous equations using data from the tables as follows;

Φ-1 ( 0.70 ) = 0.5244
180 = μ + 0.5244 σ

Φ-1 ( 0.15 ) = – 1.036
140 = μ – 1.036 σ

(Subtracting one equation from the other)
40 = 1.5604 σ
σ = 25.63, μ = 166.55

For part 3 it would be two tailed due to the double inequality, so

Φ-1 ( 0.975 ) = 1.96

Plugging this value into the normal z equation gives

a = 166.55 – 1.96 × 25.63 = 116.3
b = 166.55 + 1.96 × 25.63 = 216.8

Hope this helps

Reply 59

HannahGolton

Should answers always be given to 3sf or 4sf? Would you lose marks by giving it to the wrong degree of accuracy?