Interpreting table 1 in clinical research papers Am new to clinical research and starting off by reading some clinical papers.
In the paper, I came across a table like as shown below

Am I right to understand that the value of HbA1c can range from 6.2 to 9.2
Is that the meaning of (1.5)? Similarly for other measurements as well we have items in the bracket
Can help me understand this?
 A: No, your table means that the mean of HbA1c is 7.7 (in %), and that the standard deviation (SD) is 1.5 (again in %). The range will usually be much wider than 6.2-9.2%.
To be honest, the table is a little confusing. If they write "mean $\pm$ SD" in the caption, they should also write "$7.7 \pm 1.5$" in the table. Or conversely, they should write "mean (SD)" in the caption.
Note that sometimes people do include the range, but from what I have seen, the mean and SD is more common.
A: The first line in your picture says "mean +/- SD" so it seems reasonable to assume, that the mean HbA1c was 7.7% with a standard deviation of 1.5% and the mean Cholesterol was 4.9mmol/L with a standard deviation of 1.0mmol/L
The standard deviation is the square root of the variance an thus a measure of the amount of variation or dispersion around the mean. A small value implies that most values were close to the mean, a large value means that the spread around the mean was large.
First you compute the difference of each value from the mean and then you square that. Then you compute the mean of the squared differences and take the square root from that. Voilà, that is your standard deviation or SD.
If those values were normally distributed you could draw more conclusions from that but biomarkers are usually not normally distributed. So take it as no more or less then a way to give you an idea, whether values were generally close to the mean or not.
