A doctor asks three of her patients to measure and record their blood

Question

https://gmatclub.com/forum/download/file.php?mode=view&id=60208 A doctor asks three of her patients to measure and record their blood pressures every day for 7 consecutive days. Each patient recorded his or her systolic and diastolic pressure once each morning. The results are presented in the graph. From each drop-down menu, select the option that creates the most accurate statement based on the information presented in the graph. 1. The correlation between the systolic and diastolic pressure readings is weakest for Patient GRAPH_1_PLACEHOLDER . 2. The standard deviation of systolic blood pressure readings among the patients was lowest on Day GRAPH_2_PLACEHOLDER . 2.jpg

rocky620 · Accepted Answer

From each drop-down menu, select the option that creates the most accurate statement based on the information presented in the graph.
  
 1.1 The correlation between the systolic and diastolic pressure readings is weakest for Patient ____________. 
Kindly refer the image for details:

Patient-A  
We can see that there is a clear positive correlation between the systolic and diastolic pressure. With an increase in systolic pressure there is an increase in diastolic pressure.

Patient-B  
No proper inference can be drawn about the correlation. Even when the the systolic pressure is increasing the diastolic pressure is decreasing on Day 4 & Day 7, and vice versa is the case on Day 3 & Day 6.

Patient-C  
We can see that there is a positive correlation between the systolic and diastolic pressure. When the systolic pressure is increasing the diastolic pressure is either increasing or constant, but in no case the diastolic pressure is decreasing.

So, Option B.

A. A
  B. B  
C. C

1.2 The standard deviation of systolic blood pressure readings among the patients was lowest on Day __________.

The standard deviation will be minimum when the pressure readings are closer to one another. We can find the range and and arrive at the conclusion.
On this basis the range of systolic pressure on:

Day-1  - 70
 Day-2  - 40
 Day-3  - 30
 Day-4  - 19
 Day-5  - 29
 Day-6  - 22
 Day-7  - 11

A. 3
B. 5
C. 6
  D. 7

So, the correct answers are B & D

kntombat · Answer

Are the answer to the questions C and D ?

Sajjad1994 · Answer

Its B and D

Thank you!

kntombat · Answer

Could you post the OE please as and when possible.

sallyabdul · Answer

Thanks! How is it B and not C? I'd love to get the explanation too

sallyabdul · Answer

rocky620

I finally get it - thank you so much!!!!

Purnank · Answer

The standard deviation will be lower when points are closer to each other on the graph.

Is my logic correct? @Experts if you can help.

anand123prk · Answer

That is correct. That is to say, points will be closer to the mean.

Purnank · Answer

Thank you!

palak2110 · Answer

How is range related to SD in question 1.2 below? We found range for each of the Day 1-7 and determined the lowest SD to occur when the range is the lowest. Are range & SD positively correlated?

poojaarora1818 · Answer

Solution: 1. The correlation between the systolic and diastolic pressure readings is weakest for Patient --- Option B: Patient A shows a strong positive correlation between the  systolic and diastolic pressure, Patient B shows no relation, whereas Patient C shows a strong positive correlation.

2. We have to determine the standard deviation of systolic blood pressure readings among the patients was lowest on which day. In my opinion, SD considers how far each value is from the mean. 2) Frequency of each value. However, a smaller range suggests that a smaller SD is not necessarily true. The distribution of the values between the minimum and maximum also matters. I need an expert's advice on this. Anyone could provide their insights on it.

rjvtyagi96 · Answer

A simple trick for second part is to note where on the systolic graph, the three data points related to the three patients are most cluttered (closer to each other).
This is giving less deviation from the mean. Hence, lowest standard deviation.

A doctor asks three of her patients to measure and record their blood

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A doctor asks three of her patients to measure and record their blood

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