Official Thread: OCR MEI S2/M1

Should've been 1.74 from memory?..

Yeah I got 1.74

Yes. My point is that the textbook uses p and correlation. Have you noticed that?

Then did you use (mean of sample-mean)/ (sd/root n)?

I got around 62k for mean of second fan o_O anyone remember the question>?

My answers....

(idk what is up with latex...)



$2.[br]- \, \mathrm{'random' \, means \, each \, gene \, has \, an \, equal}[br]\mathrm{chance \, of \, mutation}[br]\mathrm{'independent' \, means \, one \, gene \, mutating \, does}[br]\mathrm{not \, affect \, the \, probability \, of \, another \, mutating}[br]- \, X \sim B(20, 0.012), \, P(X=1) = 0.1908[br]- \, \mathrm{n \, is \, large, \, p \, is \, small}[br]- \, 0.0446[br]- \, 0.9826[br]- \, 0.0210 \, \mathrm{(continuity \, correction??)}$

$3.[br]- \, 0.4722[br]- \, 95.02$

$4.[br]- \, e = 15.225, \, \chi^2 = 0.6831[br]- \, \mathrm{not \, significant}[br]- \, X \sim N(5.64, \, \dfrac{3.03701}{60})[br]\bar{x} = 6.2167, \, \sigma^2 = 3.03701[br]z = \dfrac{6.2167 - 5.64}{\sqrt{\dfrac{3.03701}{60}}} = 2.5633[br]- \, \mathrm{significant}$

How did you get 3.03701 for variance?

i remeber the data exactly



If you don't use population mean to work out standard deviation but instead use sample mean ..
then you get 1.74 like everyone else here, question is which one are we supposed to use

My answers....

(idk what is up with latex...)



$2.[br]- \, \mathrm{'random' \, means \, each \, gene \, has \, an \, equal}[br]\mathrm{chance \, of \, mutation}[br]\mathrm{'independent' \, means \, one \, gene \, mutating \, does}[br]\mathrm{not \, affect \, the \, probability \, of \, another \, mutating}[br]- \, X \sim B(20, 0.012), \, P(X=1) = 0.1908[br]- \, \mathrm{n \, is \, large, \, p \, is \, small}[br]- \, 0.0446[br]- \, 0.9826[br]- \, 0.0210 \, \mathrm{(continuity \, correction??)}$

$3.[br]- \, 0.4722[br]- \, 95.02$

$4.[br]- \, e = 15.225, \, \chi^2 = 0.6831[br]- \, \mathrm{not \, significant}[br]- \, X \sim N(5.64, \, \dfrac{3.03701}{60})[br]\bar{x} = 6.2167, \, \sigma^2 = 3.03701[br]z = \dfrac{6.2167 - 5.64}{\sqrt{\dfrac{3.03701}{60}}} = 2.5633[br]- \, \mathrm{significant}$

How did you get 3.03701 for variance?

i remeber the data exactly



If you don't use population mean to work out standard deviation but instead use sample mean ..
then you get 1.74 like everyone else here, question is which one are we supposed to use

You should always use the sample mean when working out the sd, they normally say "assume the standard deviation is the same as the population" if they dont make you work it out

I have 4 queries, regarding these worded answers. Would appreciate it anyone could say if they agree/ disagree? I hate the worded ones.
1) "Define 1% significance level"
I put: "A 1% significance level means that the probability of rejecting the null hypothesis when it is in fact true is 1%/0.01"
2) "Assumptions of underlying distribution for Spearmans test"
I put something like: "There is none, as it is calculated using ranks and not the actual values, so it is not concerned with the actual underlying distribution."
3) "Define random for the mutations of genes"
I put something like: "Mutations being random means that their occurences are unpredictable."
4) "Define independent for the mutations of genes"
I put something like: "Mutations being independant means that the occurence of one mutations does not effect the probability of another mutation occuring."

They're all a little weird to me, not sure?

Other than that I think I got all the marks, but I'll be very upset if I got these wrong.

For the meaning of random, could you also have said "The event that a gene mutates cannot be predetermined"?

1,3,4 are pretty much exact same answers me, i'm pretty sure they are model answers ... i got them from mark scheme

I think it's worthy to tell you that 1.7427^2 = 3.0370