Question

More stats Please help?! Medal/Fan

Answer 1

@Luigi0210

Answer 2

@paki

Answer 3

would 9 be a?
I know that 0.41 and 0.59 add up to 1.... but what would I do to solve?

Answer 4

10... I think this is B or C

Answer 5

@kirbykirby
@mathslover

Answer 6

For independent probabilities, p(both) = (p1)(p2)

Answer 7

"Both Lights are Green" is a subset of "The first light is green".



See how "Both" divides "first" into two sections? What percent of "First" is "Both"

Answer 8

For independent events,
\(\Large P (A \cap B ) = P (A)P(B)\)

Answer 9

0.59 = 0.41 x

Answer 10

okay, so @tkhunny
0.96

@hartnn would that be 1.43

@douglaswinslowcooper so I would multiply them?

Answer 11

0.96 is not correct. Try that again. Show your work.

Answer 12

oops, that was supposed to be
0.41 = 0.59 x

Answer 13

because for both, its 0.41

Answer 14

oh, so maybe 0.41/0.59 = 0.69 @tkhunny ?

@hartnn are you saying solve for x by dividing 0.41 by 0.59?

Answer 15

Please look closely at those two questions. Seem rather similar, don't they? I think you have the arithmetic.

Answer 16

so for the second question, I got
75 +/- -16.25 * (8/ sqrt(205)) = 65.92 - 84.08 .....

Answer 17

that seems too wide a range :|

Answer 18

@mathmale

Answer 19

Where did you get 16.25?

A -
B - Not symmetrical about the mean. Throw it out.
C - Not symmetrical about the mean. Throw it out.
D - Does not contain the mean. Throw it out.

That's odd. There's really only one to choose from, due probably to intent or poor authorship. You need calculate nothing if you would like the correct answer without arithmetic.

Answer 20

oh, wow, that seems really easy O.o
and I think 16.25 was the z score .....

Answer 21

16.25 is NOT a Z-score. You should find 1.96, somewhere.

Answer 22

Oh... O.o I must have plugged in my numbers in wrong then

Answer 23

Regarding the first question:

oh, so maybe 0.41/0.59 = 0.69 @tkhunny ?

@hartnn are you saying solve for x by dividing 0.41 by 0.59?

You're on the right track. How about writing out the formula you're using, and naming it?

Answer 24

whats the formula for finding 95% confidence interval ?

Answer 25

Regarding your "so for the second question, I got
75 +/- -16.25 * (8/ sqrt(205)) = 65.92 - 84.08 ..... "

where did that 16.25 come from, and why is it negative?

Answer 26

Or, better yet, what's the general formula for a confidence interval for use in "capturing" the true population mean?

Answer 27

i don't even know what confidence is....except for its usage in english :P

Answer 28

this is what I did....
x¯=75
σ=8
n=205

and the formula (x - n)/σ ....

Answer 29

\[ xbar \pm (z ~critical~value)*(\sigma \sqrt{n)}\]

Answer 30

is that for z score?

Answer 31

So, Melissa: you'll need to find the "z-critical value" for a confidence level of 95%. What is it? How do you calculate or otherwise find it?

Answer 32

is it like saying "I am 95% confident that HBPM will be in the interval 73.9 - 76.1"

Answer 33

I thought it was ^^

Answer 34

x¯=75
σ=8
n=205

and the formula (x - n)/σ ....

Answer 35

@hartnn: Strictly speaking, here's what "confidence" would mean, in context: "Were we to take independent samples of size 205 from the general population again and again, then 95% of the time, our confidence interval would capture the true population mean."

Answer 36

@MelissaHolmes : The formula you've provided is for z-score.

The "z-critical value" has to do with the level of confidence you're interested in. In this problem you want a 95% confidence interval. The associated z critical value is 1.96. Think back: Have you seen this before? We can (1) memorize z-critical values for various levels of confidence, or (2) calculate them, or (3) look them up in a table.

Answer 37

OHHHHHHHHHHHHHH...... oh my goodness, that's why I got it wrong >.< I thought I had to use z score O.o

Answer 38

Important that you know this material.

Please look at

http://www.math.armstrong.edu/statsonline/5/5.3.2.html

Answer 39

i found another good reference
http://www.ucd.ie/statdept/classpages/introquantmeths/introqmchp12.pdf

Answer 40

ok, thank you so mathmale and hartnn! :D

Answer 41

\[xbar \pm (z ~critical~value)*(\sigma \sqrt{n)}\] Now please replace xbar with 75, "z critical value" with 1.96, sigma with 8 and n with 205.

Answer 42

You're very welcome!

Answer 43

:D

Answer 44

for xbar range shouldn't we use sigma/sqrt(n),. standard error of the mean,
rather than sigma*sqrt(n) ?

Answer 45

@douglaswinslowcooper : Good question. In this type of question, the population standard deviation is usually unknown, and thus one has to use S, the sample std. dev. But in THIS particular problem, the population std. dev. is given, and so I thought to use it. What do YOU think in this particular situation?

Answer 46

I am fine with using the population standard deviation, SD,
but to get a confidence interval for the mean, I'd use the standard error
SE = SD/sqrt(n). then use the usual multipliers [e.g., 1.96] because means are even more nearly normal than the distributions from which they are obtained.