The first one is correct but the second is not.
P(Studied for 4 hours OR Expects a B) = 0.12 + 0.06 + 0.12 + 0.02 + 0.21 in R gives:
> 0.12 + 0.06 + 0.12 + 0.02 + 0.21
Expected Grade E.G E.G E.G Studied More Than 4 Hours A B C D YES 0.12 0.06 0.12 0.02 NO 0.13 0.21 0.26 0.08
a) this student studied more than 4 hours and expects a B
b) this student studied more than 4 hours or expects a B
this is what i got:
I thought question (a) was straightforward so I just assumed the probability would be same as the percentage of students thats studied more than 4 hours and expected a B which was 0.06
For question (b) I got P=0.32 by simplying adding all the percentages of students that studied more than 4hours which was 0.32 and because within the 0.32 percentage the students who expected B were included, I'd assumed we just leave it at 0.32.
I just wanted to make sure if I answered them correctly, if not what did I do wrong :s
Thanks in advance for reading and helping