MHB Probability Activity Word problem for relative frequency

[bke0712]

I am drowning in math right now and would love some help bc I am horrible at math.

Here is what I have got.

Question:
1. The four major blood groups are designated A, B, AB and O. Within each group there are two types; positive and negative. Find data on the relative frequency of these eight blood groups (as in the general population).
a. Make a table showing the probability of meeting someone in each of the eight groups.
b. For a group of 50 people, how many would you expect to have in each one of these groups?

I have gotten this info :

ABO Type Rh Type
O positive 37.4%
O negative 6.6%
A positive 35.7%
A negative 6.3%
B positive 8.5%
B negative 1.5%
AB positive 3.4%
AB negative .6%

Please help, I have 5 projects to complete by tonight in Statistics and ready to cry. TIA.

 

[topsquark]

What have you been able to do so far? (You need to show your work on this Forum as well! (Wink) )

-Dan

 

[Jameson]

Hi bke0712,

Welcome to MHB! :) As topsquark wrote, showing us what you've done so far is very helpful and something we like to see before helping. That said, here are some initial comments.

Ok so it looks like you have found the data you need. For (a), I would just convert the percentage to a probability scale. Percentages are from 0 to 100 (with data like this at least) and probabilities are from 0 to 1 (always). So you should convert your numbers to a new scale by dividing each number by 100. For example, 35% corresponds to 0.35.

For the last part, we're going to use this logic. $E[X] = X \cdot P[X=x]$. That looks scary maybe but all it means is that to find the expected number of people we take the number of people times its probability.

 

[bke0712]

.374 x
.066 x
.357 x
.063 x
.085 x
.015 x
.034 x
.06 x

= X \cdot P[X=x]$. That looks scary maybe but all it means is that to find the expected number of people we take the number of people times its probability.

This is where I get confused.

 

[Jameson]

Ok looks good! What are the x's for? You can just use the decimals. :)

For the expected number out of 50, just multiply. If you have 50 people, then we would expect .374*50=18.7 of them to be O-positive. Keep going down the line for the other expectations.

 

[bke0712]

so for the answer to a. and b. I am multiplying?

wouldn't that be the same answer to both? ugh math.

 

[HallsofIvy]

so for the answer to a. and b. I am multiplying?

In a problem like this "probability" is the same as percentage. Yes, to find a percentage of a particular number, you multiply the percentage, written as a decimal, by the number.

wouldn't that be the same answer to both?

No, it wont. The answer to the first problem is a decimal number, less than 1. The answer to the second is that decimal multiplied by 50.

ugh math.

Do you think it is a good idea, when asking people to help you, to insult them?