There are ______volunteers for the research study on the gggg. Each subgroup of the study will contain _____participants. Determine how many ways these participants can be selected and explainour method.

- anonymous

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- anonymous

nCr=n factorial over r factorial times n minus r factorial<---this is the formula we use

- jim_thompson5910

that's only if you had 2 subgroups

- jim_thompson5910

but we actually have 40/10 = 4 subgroups

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## More answers

- anonymous

Oh okay:)

- anonymous

wouuld we use permutations?

- jim_thompson5910

I'm not sure, but I'm still thinking

- anonymous

kk:)

- anonymous

i can ask another question if u don't know this one:)

- jim_thompson5910

yeah I'm stumped, but I'll still give it some thought. What is your other question?

- anonymous

The study participants were divided into four groups—two groups received the Power Pill (Group A and Group B) and two groups received a placebo (Group C and Group D). The effects of the Power Pill were measured. One group that received the Power Pill (Group A) and one group that received the placebo (Group C) were told of the anticipated effects of the Power Pill—accelerated hair growth—while the other two groups (Group B and Group D) were not provided with this information. All four groups were told to monitor and report any physical changes during the study.
Results were reported and participants were grouped as to either “Saw Results,” meaning that participants reported increased hair growth as part of physical changes during the study, or “No Results,” meaning that increased hair growth was not mentioned as part of physical changes during study.
Results are as follows:
6 in Group A saw results.
7 in Group B saw results.
5 in Group C saw results.
4 in Group D saw results.
Part 1:
Create a two-way table for the data and find the probabilities for each group. Describe results in terms of the study.

- anonymous

it isnt actually that bad this question

- jim_thompson5910

hmm I guess if you group it into 2 groups, then you'd be right in saying you use a combination. Just think of group A and B as one group (same as C and D).

- anonymous

ok. How would the data table look then?

- jim_thompson5910

one moment

- jim_thompson5910

|dw:1446244115297:dw|

- anonymous

ok so do u want me to plug it in?

- jim_thompson5910

`6 in Group A saw results.`
`7 in Group B saw results.`
`5 in Group C saw results.`
`4 in Group D saw results.`
|dw:1446244304080:dw|

- anonymous

|dw:1446244184082:dw|
That this?

- jim_thompson5910

yep fill out the rest of the table using what steps you already did

- anonymous

|dw:1446244254840:dw|
Done!

- jim_thompson5910

looks good

- anonymous

now, how would we describe the results?

- jim_thompson5910

Then to calculate the probabilities, you simply divide each number in the box by 40
for example
the probability of picking someone from group A who saw results is 6/40 = 0.15 = 15%
the probability of picking someone from group C who did NOT see results is 5/40 = 0.125 = 12.5%
etc etc

- anonymous

Oh okay! But wait!

- anonymous

What is the probability that a person saw results, given they received the Power Pill? What is the probability that a person saw results, given they received a placebo? Explain in terms of the study.
This is the last part:)

- jim_thompson5910

ah I see now

- jim_thompson5910

`What is the probability that a person saw results, given they received the Power Pill?`
focus on the "power pill" people only. So exclude those who did NOT receive the pill. So we exclude groups C and D and only focus on A and B

- jim_thompson5910

|dw:1446244755508:dw|

- jim_thompson5910

how many people saw results? out of what total amount of people?

- anonymous

would i divide 6 by 10?

- jim_thompson5910

there are 6+7 = 13 people who saw results out of 10+10 = 20 people total
13/20 = 0.65 = 65% is the probability of picking someone who got results given we know they received a power pill

- jim_thompson5910

|dw:1446244904638:dw|

- anonymous

Wait! Lol I didn't get the explanation :(

- anonymous

Then would the placebo be 45%?

- jim_thompson5910

do you see how I'm just focusing on columns A and B?

- anonymous

yes!

- jim_thompson5910

in those columns, we have 6+7 = 13 people who saw results (first row)
this is out of 10+10 = 20 people (last row) total in group A or group B
so 13/20 = 0.65 = 65%

- jim_thompson5910

What is the probability that a person saw results, given they received the Power Pill?
The answer here is 65% or 0.65 or 13/20 (depends on what format the teacher wants)

- anonymous

Ohh! Ok! So then the placebo would be 45%?

- anonymous

9/ 20= 45%<---people who got the placebo right?

- jim_thompson5910

`What is the probability that a person saw results, given they received a placebo?`
yes the answer is 9/20 = 0.45 = 45%

- anonymous

Yay! Ok then, What is the probability that a person received the placebo, given that they did not see results?

- anonymous

would it be 11/ 18?

- jim_thompson5910

`What is the probability that a person received the placebo, given that they did not see results?`
key phrase: given that they did not see results
so we focus on the "did not see results" row only
|dw:1446245252897:dw|