# CAHSEE Math 2.4 Statistics, Data, and Probability I

Statistics, Data, and Probability I: Drill Set 2, Problem 4. Which of the following statements is true?

 CAHSEE Math Statistics, Data, and Probability I Language English Language Statistics Charts, Graphs, and Tables Statistics, Data Analysis, and Probability 6 Data sets

### Transcript

00:27

So... when a question asks us anything like "which of the following are true",

00:31

it means we just have to roll up our sleeves and go one by one testing each little morsel

00:36

of hot dog they give us to evaluate. Let's just start with A.

00:39

It says, "more than half the students took between 15 and 45 minutes"

00:45

So then we just go back to the pie chart thing and see what it has to say.

00:49

Everything here is in percents, so to make things easier on ourselves, we can just think

00:53

about it as a number of students rather than some fancy fraction.

00:57

And in this case we can throw out answer A immediately because

01:00

57% took 45 minutes to an hour...

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...that is, since over half DIDN'T fit in the 15 to 45 minute time window,

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there's no way that more than half COULD.

01:12

We don't get brownie points for calculating that 10% took 15-30 minutes

01:16

and 23% took 30-45 minutes for a total of 33%.

01:22

So let's throw out A and move on as fast as we can.

01:25

B is sorta the counter-side of A.

01:28

It says LESS than half the students took 45 minutes to an hour to fnish...

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...but we just noted that this number was 57% ... already OVER half.

01:38

So B is a quick easy toss out.

01:40

Move on to C.

01:41

C says: More than a quarter of the class took

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EITHER 15 to 30 minutes to finish, OR did not finish the test at all.

01:49

So here, we've got a SUM. Meaning... we ADD both cases.

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That's what happens when we have a conditional phrase like "OR".

01:57

As in... Hand me a condiment --

01:59

either that half gallon jug of ketchup OR that gallon jug of mustard.

02:04

So in the 15-30 minute group, we see that 10% of the students were captured here --

02:09

and then in the Did Not Finish group, we have 10% as well.

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If we add them, we have a total of 20% of the students in those two groups.

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So C is in fact only 20%, which is LESS than a quarter or 25%.

02:22

So C ain't cuttin' it for us either. Odds are very good D is the answer.

02:27

D says that more than a quarter of the class took between 15 and 45 minutes to finish.

02:33

Well, the 15-30 group was 10% - check.

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And the 30-45 group was 23% - check.

02:40

ADD the two groups to get 33% and yeah -- woo hoo --

02:44

33% is in fact greater than a quarter or 25%

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So the answer is, yes... we can read a pie chart. D.

02:53

Time for a slice.