so confused

[pale terrace]

1. Ask your question and show the work you've done so far. If you've posted a screenshot of a question, specify which part you need help with.
2. Wait patiently for a helper to come along.
3. Once someone helps you, say thank you and close the thread with:

   +close
   

4. Feel free to nominate the person for helper of the week in #helper-nominations
5. Do not ping the mods, unless someone is breaking the rules.
6. If you're happy with the help you got here, and the server overall, you can contribute financially as well:

[upper wraith]

I know how to do a, b and c

but d is the one that just confuses tf out of me

if it's guilty of fraud OR family owned

A.KA

P(A U B)

then isn't the answer 50/100?

because of guilty of fraud is 10

and family owned is 40

so 40 + 10 = 50/100??

[upper wraith]

hello

[vapid parrot]

@upper wraith i have a different way to do (d)

It's lengthy but understandable

[upper wraith]

is the answer 44/100?

[vapid parrot]

Wait lemme calculate

[vapid parrot]

Yes

[upper wraith]

I was just overcomplicating it

i just did 6 + 34 + 4

which is 44

but there's an equation I can use too which the exam probably wants me to use

P(A) + P(B) - P(A n B)

[upper wraith]

yeah this is probably the exams preferred way

[vapid parrot]

See this method two

[vapid parrot]

Yea

[upper wraith]

im doing this now

can I give the answers and you can cross check?

[vapid parrot]

Similar ques

[vapid parrot]

Oh okay

[upper wraith]

I'll start with 1 which is easy

it's just 82/100

/200*

which is 41/100

so the probability that the population is employed is 41%

no wait

scratch that

I made a mistake

employed is 82 + 32

which is 114

114/200

is 57/100

so it is 57%

now for question 2:

82 + 38 = 120/200

60/100

= 60% that support bike schemes

part c now

[vapid parrot]

Correct

[vapid parrot]

Correct

[upper wraith]

The question can be codified as computing the probability that both events "E" and "B" occur - "E" being those employed and "B" being those who support bike schemes.

I.e : The joint probability of both "E" and "B". From the table, we can see that this is 82/200 which is 41/200 = 41%

i.e the probability of the population being both employed and supporting bikes are 41%

[vapid parrot]

Correct

[upper wraith]

part d now

the question can be codified as computing the probability of event "B" given event "E" occurs.

i.e: the conditional probability.

We can use this following equation:
P(E n B)/P(B)

In other words: P(82)/P(120)

82/120

Which is 68%

[vapid parrot]

Wrong

[upper wraith]

i knew it

wait let me try again

fucking hate these equations

given that he/she is emplyed

ohhh I used the wrong fomula

it's P(E n B)/P(E)

so 82/114

which is 72%

[vapid parrot]

P(emplyoed) = 114/200

[vapid parrot]

Yes

[upper wraith]

nice

lets try e now

this question can be codified as computing the probability thaat either event "B" or event "E" does not occur. We can solve this by using the additional rule:

P(E) + P(B) - P(E n B"

However we will first have to work out the probability of the "not employed" and "not supporting bike schemes"

48 + 32 = 80/200 which means 0.40 do not support bike schemes.

48 + 38 = 86/200 which means 0.43 are not employed.

Now the probability that they are not employed AND do not support bike schemes is 48/200 which is 0.24.

So let's re-formulate the equation.

0.40 + 0.43 - 0.24 = 0.59

i.e 59% of the population in the above table does not support a bike share scheme or is not employed.

I could've easily just done 38 + 48 + 32 which is 118/200 which is 59% but probably woudn't get full marks

time to try part F

yes, these are independent as the occurrence of "being employed" has no effect on the occurrence of "supporting bike-scheme" and vice versa too.

[upper wraith]

is there a better way to answer this bc I don't think this will get me 5 marks

[vapid parrot]

Bruhh

There is also a mathematical method to prove events are independent or not

If P(A).P(B) = P(AnB) then A and B are independent

What you got in e) ??

You got 59% ?? It's wrong

[upper wraith]

really?

what's the correct answer?

[upper wraith]

but I used the correct formula

[vapid parrot]

I got 18%

[upper wraith]

can I see your working

[vapid parrot]

I don't have now shit

[upper wraith]

I don't understand this equation

[vapid parrot]

Lemme type it

[upper wraith]

can you explain it with the numbers above

[vapid parrot]

Bro actually if this equation satisfyies

Then

A and B are

Independent

[upper wraith]

yh ik

but idk how the equation works

[vapid parrot]

Oh actually i forgot the concept behind it sorry

It was derived from conditional probability

[upper wraith]

so 57*41?

[vapid parrot]

??

Wait , first let's do e

[upper wraith]

ok

[vapid parrot]

Send the ques again

I can't scroll now

[upper wraith]

ok

[vapid parrot]

@upper wraith

[upper wraith]

letter e

[vapid parrot]

We need to find P(S'UE')

There is a formula , P(S'UE') = P(SnE)' = 1-P(SnE)

[vapid parrot]

It can be derive from venn diagram

1-82/100 = 18/100 = 18%

[upper wraith]

i think that's wrong

my uni teaches it like this:

[upper wraith]

this is the solution sheet to this question:

[vapid parrot]

It's a different question

[upper wraith]

yeah but the same formula applied

the P(A U B) = P(A) + P(B) - P(A n B)

[vapid parrot]

It means calculation is wrong either

[upper wraith]

Plus I double checked using the lazy way which is 38 + 48 + 32

and it also gave 59%

[upper wraith]

same which this, if you use the lazy way you get the same answer too (34 + 6 + 4)

44%

[vapid parrot]

What's the answer in answer key??

[upper wraith]

wdym

[vapid parrot]

I did correct, i don't know how's this happening

[vapid parrot]

I mean what's the correct answer??

[upper wraith]

most likely my one

[vapid parrot]

For e

[upper wraith]

because even if you double check, it gives the same answer

let's move on

so about the independance thing

this is what my uni said:

but I don't get this formula

or how to apply it to the employment/bike scheme table

[vapid parrot]

Try

[upper wraith]

ok so P(A) is 114/200

and P(b) is 120/200

and P(A n B) is 82/200

so does that mean 114/200 * 120/200 = 82/200?

that doesn't make sense

[vapid parrot]

🤦🏻

[upper wraith]

what

[vapid parrot]

Actually

Ah

57/100× 60/100 ≠ 41/100

So they are not independent

[upper wraith]

I see but how does that make sense from a rational point of view

being employed and supporting bike schemes don't relate to eachother

the occurence of one event happening will not effect the occurence of the other event

[vapid parrot]

Yep it's a theoretical way

But we are studying mathematics

We need equations and theorems to prove a thing

[upper wraith]

ah

[upper wraith]

ok now the hard questions

the ones that mess with my brain

[vapid parrot]

I don't have any interest in stats

Haha

I don't study it also