# I need help

Hello,
I was wondering if someone could help me this. Why standard error of mean is higher for blood pressure in standing pressure and lower in supine position? I am really stuck with this and your help will be appreciated.
Thanks
When you do a study among a population of people, the subjects should be randomly chosen. Say you choose 100 people, you measure their blood pressure while standing and then repeat for the same people while supine (lying down), and then get an average for both.
Imagine you do this 10 times so you test 100 x 10 = 1,000 in total and you get 10 averages for standing and 10 averages for lying down, one for each of the 10 groups. Then you add the 10 standing blood pressure averages together and then average that so you have the average of all 1,000 people.

Do you think the average of 1,000 people is going to be the same as each of the 10 averages of groups of 100 people?
Unlikely.

Standard error is the how different the population average is to the individual sample average.

If you chose 100 people randomly, and you do that 10 times, you are going to get a wide range of heights for people. Someone might be 1.9m tall while another is just 1.4m tall. That's 50cm difference. The blood pressure will vary significantly based on the person's height and size, when they are standing up and the heart has to pump against gravity.

But when they are lying down, the difference in height/how hard the heart has to pump against gravity, is not so different no matter how tall or short a person is. There will be a difference, but not as big as standing BP. So the answer is basically due to the varying heights of people (max height blood needs to be pumped) when standing vs body thickness (max height blood needs to be pumped).

Hope that helps.
(edited 1 year ago)
Original post by martinthemartian
When you do a study among a population of people, the subjects should be randomly chosen. Say you choose 100 people, you measure their blood pressure while standing and then repeat for the same people while supine (lying down), and then get an average for both.
Imagine you do this 10 times so you test 100 x 10 = 1,000 in total and you get 10 averages for standing and 10 averages for lying down, one for each of the 10 groups. Then you add the 10 standing blood pressure averages together and then average that so you have the average of all 1,000 people.

Do you think the average of 1,000 people is going to be the same as each of the 10 averages of groups of 100 people?
Unlikely.

Standard error is the how different the population average is to the individual sample average.

If you chose 100 people randomly, and you do that 10 times, you are going to get a wide range of heights for people. Someone might be 1.9m tall while another is just 1.4m tall. That's 50cm difference. The blood pressure will vary significantly based on the person's height and size, when they are standing up and the heart has to pump against gravity.

But when they are lying down, the difference in height/how hard the heart has to pump against gravity, is not so different no matter how tall or short a person is. There will be a difference, but not as big as standing BP. So the answer is basically due to the varying heights of people (max height blood needs to be pumped) when standing vs body thickness (max height blood needs to be pumped).

Hope that helps.

Than you so much for the answer. There were 50 individuals they did participate -now I have SEM(standard error or mean) for diastolic and systolic blood in supine position -1.05 and 1.48 respectively along with SEM for MAP(mean arterial blood pressure) for supine 1.05.
SEM for diastolic and systolic standing blood pressure is 1.7 and 2.5 respectively and also SEM for MAP(standing) is 1.64. How I can explain this data distribution in simple words please. Once more thank you.
Original post by Dani69
How I can explain this data distribution in simple words please.

What do you want to say exactly? Do you just want to state the results of the various SEMs in words and sentences or did you want to explain why the SEM has a big difference between standing and supine position?

If you just want to state the results, you can simply state it, but in complete sentences. For example:
"The diastolic and systolic blood pressure in [position 1] was ____, and the diastolic and systolic blood pressure in [the other position] was ____.

If you want to "explain" ("explain" questions require you to mention an effect/observation and state a reason(s) for that observation), then you can say what the results were (see the sentence example above) and then say something like "The difference in the blood pressure measurements for [position 1] and [position 2] may be due to ____" and add the reasons based on what I already explained (body height, body size etc) and what you know about the things that can affect blood pressure.
Original post by martinthemartian
What do you want to say exactly? Do you just want to state the results of the various SEMs in words and sentences or did you want to explain why the SEM has a big difference between standing and supine position?

If you just want to state the results, you can simply state it, but in complete sentences. For example:
"The diastolic and systolic blood pressure in [position 1] was ____, and the diastolic and systolic blood pressure in [the other position] was ____.

If you want to "explain" ("explain" questions require you to mention an effect/observation and state a reason(s) for that observation), then you can say what the results were (see the sentence example above) and then say something like "The difference in the blood pressure measurements for [position 1] and [position 2] may be due to ____" and add the reasons based on what I already explained (body height, body size etc) and what you know about the things that can affect blood pressure.

Thank you Martin and much appreciated. Amazing explanation
Original post by Dani69
Thank you Martin and much appreciated. Amazing explanation

You're welcome! Glad it helped. Would appreciate an upvote if you can 😃
How do i do upvote pls>
Original post by Dani69
How do i do upvote pls>

I think you already have. You click on the thumbs up icon on the bottom left of each post.
Original post by martinthemartian
I think you already have. You click on the thumbs up icon on the bottom left of each post.

You are more than welcome. Are you student as well?
Original post by Dani69
You are more than welcome. Are you student as well?

Not at the moment, I just quit a masters program that wasn't the way I thought it would be so now I am revising for an exam to do a graduate entry degree.
Original post by martinthemartian
Not at the moment, I just quit a masters program that wasn't the way I thought it would be so now I am revising for an exam to do a graduate entry degree.

is it medicine or?