Question

help, see attachment

Answer 1

you use a table like this one http://www.icess.ucsb.edu/gem/material_clima_I/normal01.jpg

Answer 2

still dont understand

Answer 3

P(Z>b) is the area to the left of b, P(Z<b) is the area to the right of b

Answer 4

what about P(Z>b) = 0.0735?

Answer 5

i have those backwards

Answer 6

P(Z>b) is the area to the right of b, P(Z<b) is the area to the left of b

Answer 7

P(b less Z less 0.55) = 0.2487?

Answer 8

P(Z>b) = 1 - P(Z<b) so find P(Z<b)=1-.0735

Answer 9

look on the chart for the b which gives .9265

Answer 10

but there is no .9265

Answer 11

it's there

Answer 12

the answer is 1.45

Answer 13

why don't we just look at it directly

Answer 14

i got - 1.45

Answer 15

?

Answer 16

for part b?

Answer 17

yes

Answer 18

it should be +1.45

Answer 19

what about part c?

Answer 20

break it up into 2 parts

Answer 21

P(b<Z<.55)=P(Z<.55)-P(Z<b)

Answer 22

P(Z<.55) = .7088

Answer 23

so P(Z<b) = .7088-.2487

Answer 24

P(Z<b) = .4601

Answer 25

ok, what about the part 4

Answer 26

P(-b < Z < b) = 2 * P(.5 < Z < b)

Answer 27

P(.5 < Z < b) = .7415 / 2 = .3708

Answer 28

which one is correct, are you doing part c?

Answer 29

which is equivilent to finding P(Z < b ) = .8708

Answer 30

which one is correct, are you doing part c?

Answer 31

from the table, b = 1.13

Answer 32

part d

Answer 33

what about part c?

Answer 34

part we had P(Z<b) = .4601

Answer 35

part c

Answer 36

find P(Z<b) = (.5 - .4601) + .5, then flip the sign

Answer 37

P(Z < b) = .5399, b = 1.0
so the answer to part c is -1.0

Answer 38

so cunfused now

Answer 39

wait

Answer 40

it's -0.1, read the chart wrong

Answer 41

you need to learn how to use the chart XD

Answer 42

for the part d , where did you get that .5?

Answer 43

because the chart is symmetric you just find the right half and multiply by 2

Answer 44

so the answer is 1.13

Answer 45

?

Answer 46

yes

Answer 47

thank you very much

Answer 48

can you explain one more question?

Answer 49

sure

Answer 50

that's very similar

Answer 51

convert the grades to zscore with (grade - mean)/stddev then use the table to find probabilities

Answer 52

can you take first one as an example?

Answer 53

z = (55.5-67)/7 = -1.643
Find P(Z < -1.643)

Answer 54

but there is no -1.643?

Answer 55

the chart only gives half the values because it's symmetric

Answer 56

P(Z < -1.643) = P(Z > 1.643)

Answer 57

P(Z > 1.643) = 1 - P(Z < 1.643)

Answer 58

what is P(Z < 1.643) from the table ?

Answer 59

about .95

Answer 60

so the answer is 1-.95 = .05

Answer 61

oh ok

Answer 62

for the second one i got 0.6443

Answer 63

that is P(Z < .37) you need P(Z > .37)

Answer 64

0.7357?

Answer 65

nope

Answer 66

P(Z < b) + P(Z > b) = 1

Answer 67

1-0.37?

Answer 68

1-.6443

Answer 69

0.3357

Answer 70

that's it

Answer 71

third one

Answer 72

how to find that one?