Question

Find the area under the normal distribution curve between z = 1.52 and z = 2.43

Answer 1

You can use a TI-83/84/89 etc or you can use wolfram alpha

http://www.wolframalpha.com/input/?i=normalcdf%281.52%2C2.43%29

to get

P(1.52 < Z < 2.43) = 0.05671

Answer 2

thank you!

Answer 3

yw

Answer 4

ugh I hate math! This is my hardest class ever

Answer 5

just take things one step at a time

and know that there are tons of tools out there to help

Answer 6

like this calculator for instance

Answer 7

Punching in a simple command in your calculator to determine the area sounds a heck of a lot easier than manually evaluating a Gaussian integral, so don't take that for granted...

Answer 8

well you need calculus for that oldrin.bataku...which I'm assuming HelloAshley hasn't learned yet

Answer 9

That's my point! :-p this class while it may seem challenging is a lot easier now than it might've been 60 years ago.

Answer 10

I haven't taken a full class of calculus. I'm in my survey of mathematical methods. I'm basically learning all types of math. It jumps around a lot

Answer 11

sounds like an interesting class, never had anything like it

Answer 12

it's really hard. I'm terrible at math and it's a super fast paced class and we don't get to spend enough time on each type of math so it is very demanding

Answer 13

@HelloAshley well if you ever need anything you can always ask for explanations here!

Answer 14

is it one of those courses where it's all crammed into 5-7 weeks?

Answer 15

I wish I would have known of this much sooner. I only have one assignment left until I am done with the class. Thank God! Yes it is all crammed into 5 weeks.

Answer 16

thought so, I hate those course schedules...way too much info to squeeze into a very tight window

not much learning gets done when you're blazing through it that quickly

Answer 17

I agree! Stupid thing is that I won't use any of the math I am learning

Answer 18

yes you will (ok you might), so you never know

Answer 19

always good to keep your mind open because that's how you improve your odds of landing the job you want

Answer 20

I'm going to be a preschool teacher.

Answer 21

i see, well it still won't hurt to know some of this stuff

because you'll still need to do things like banking, borrowing money, etc

Answer 22

Find the value for the correlation coefficient r; X= 5 1 4 2 3 Y= 5 10 12 4 8. is it –0.073
–0.094
–0.203
–0.149

Answer 23

i got -0.094 but idk

Answer 24

do you have a program like excel?

Answer 25

You don't even have to use Excel... just compute the standard deviations and means. Least-squared models have coefficients that are readily computable esp. for small data sets.

Answer 26

squares**

Answer 27

no I don't have excel

Answer 28

ok how did you get -0.094 ?

Answer 29

was it just a guess or did you figure it out through some method or formula?

Answer 30

TI-83 calculator

Answer 31

ok hopefully you entered the two data sets into two lists

then you used the 2-var statistics (under the stats/calc menu) option to find the answer

it is -0.094 , so you are 100% correct

Answer 32

yay! :D thanks. I think some times I just think I'm an idiot so I just need someone to tell me I'm either right or wrong, self esteem issue I think. I'm always second guessing myself

Answer 33

well you should usually go with your instinct since it's usually correct

second guessing leads to wrong answers a lot of the time I've noticed

Answer 34

me too

Answer 35

Which of the following is not a property of a normal distribution?
It never touches the x-axis.
It is continuous.
The mean, median, and mode are equal.
It is bimodal (i.e., it has two modes). I say it's this

Answer 36

yep, it's symmetric about one peak and it doesn't have more than one peak

so it's not bimodal (and it's unimodal)

Answer 37

A data set of size 19 has correlation coefficient of r = –0.432. Test the significance of r at the 5% level and at the 1% level. I think its r is significant at 5% and at 1%. My choices are r is significant at 5% and at 1%.
r is significant at 5%, but not at 1%.
r is is not significant at 5% or at 1%.

Answer 38

have you learned about hypothesis testing?

Answer 39

yes

Answer 40

ok so what makes you think it's significant at 5% and 1% ?

Answer 41

i think its not significant at either....idk I'm confused

Answer 42

let me see if I can find a page that explains the hypothesis test we'll use, one sec

Answer 43

ok this page may help

http://rmower.com/statistics/prog_calc_stat/How_to/Hypothesis_Test_Linear_correlation_TI-83-84_Plus_TI-Inspire%20w-84_keyboard.htm

we'll be using the formula

\[\large t = r\sqrt{\frac{n-2}{1-r^2}}\]

in this case, r = -0.432 and n = 19, so...

\[\large t = r\sqrt{\frac{n-2}{1-r^2}}\]

\[\large t = -0.432\sqrt{\frac{19-2}{1-(-0.432)^2}}\]

\[\large t = -1.974979\]

Answer 44

The test statistic is \[\large t = -1.974979\]

Answer 45

thanks

Answer 46

did you manage to get this far?

we're not done since we still need the critical values

Answer 47

i get lost at this point. but i could have swore i was right with it not being significant at either

Answer 48

oh you said not significant for both? i need my eyes checked lol

yeah you're right about both, neither are significant

Answer 49

the basic idea is to find the critical values for the 1% level and the 5% level

then you see if the test statistic lies in the rejection region. If it does, then the value of r is statistically significant. If not, then it's not significant.

Answer 50

phew lol i was starting to sweat on that one. lol. I thought it was one way and then i realized i was wrong & had a hard time going back to double check and got myself all confused.

Answer 51

sadly it's kinda hard to explain, but I think that page may have an example

maybe not...just looked back at it and it just has the formulas and such

hmm maybe your lesson, videos, or notes has a better explanation

Answer 52

my video wasn't much help. I'm trying to do a pre test as a warm up to my actual final test for the class and I am sucking :( I don't get graded on my pre test but I still don't want to do bad

Answer 53

that's unfortunate, how about the notes then?

Answer 54

I hate the wording in this, it always gets me confused when they try to trick you...Which statement is true for a statistical study? The sample is a subset of the population. The population is a subset of the sample.

Answer 55

If A is a subset of B, then A is a smaller set (usually) that fits completely within the larger set B

Answer 56

i dont have notes. its just a video and example in the book. thats about it. not helpful for sure, i wish they explained more

Answer 57

example:

A = set of all mammals

B = set of all animals

every mammal is an animal, so the set of mammals is completely in the set of animals

so A is a subset of B

Answer 58

the opposite is not true since you could easily have an animal that's not a mammal (eg: snake)

so B is not a subset of A

Answer 59

so the 1st answer then?

Answer 60

idk y i find this so confusing

Answer 61

correct, the sample fits in the population

but the population doesn't fit in the sample

Answer 62

here's a venn diagram

Answer 63

thats what i thought. i can do hard math is seems easier than i can do the stuff that is supposed to be easy. i over think

Answer 64

yeah like i said, just take things one step at a time and don't panic

Answer 65

Find the area under the normal distribution curve between z = –1.34 and z = 2.95?
0.908 i think its this
0.088
0.410
0.498

Answer 66

good

Answer 67

you got it

Answer 68

Find the area under the normal distribution curve to the right of z = –1.03
0.151
–0.349
0.349 i think this one
0.849

Answer 69

http://www.wolframalpha.com/input/?i=normalcdf%28-1.03%2C5%29

Answer 70

what you want is the last row in the "probabilities" section

Answer 71

so its 0.849

Answer 72

i was way off then

Answer 73

yes 0.849

Answer 74

the 2nd time i did it i got .85 blah i drive myself nuts lol

Answer 75

lol how are you getting these answers? are you using the calc I'm using?

Answer 76

no i was using some other crap i just closed. it was too confusing. lol

Answer 77

oh which is that if I may ask?

Answer 78

For the 20 test scores shown, find the percentile rank for a score of 86.
75 63 92 74 86 50 77 82 98 65 71 89 75 66 87 59 70 83 91 73
I think its at the 70th percentile

Answer 79

that given data set sorts to

50, 59, 63, 65, 66, 70, 71, 73, 74, 75, 75, 77, 82, 83, 86, 87, 89, 91, 92, 98

Answer 80

86 is in slot #15 (out of 20 total slots)

so it's in the (15/20)*100 = 75th percentile

Answer 81

oh wait...then again there are actually 14 values below slot 15

so that would place it in the (14/20)*100 = 70th percentile

so it sounds like you're correct

Answer 82

nvm that last thought before where i got 75

Answer 83

Count all the ones that are lower than 86.

Number_of_lower_scores=14

Total_number_of_scores=20
i thought it'd be 14/20 which is 0.7 and then it's be 70%

Answer 84

so 75 is right, right?

Answer 85

i meant 70

Answer 86

i think your initial answer of 70 is more correct

Answer 87

now that I think about it

Answer 88

yeah wasn't thinking with the 75 lol

Answer 89

:)

Answer 90

If a student's percentile rank in a class of 400 students is 87, find the student's class rank

Answer 91

i say 52

Answer 92

same data set?

Answer 93

oh wait nvm

Answer 94

choices
40
44
48
52