Interpreting Data Flashcards
How do you calculate standard deviation?
Take the mean - Distance from the mean, squared
When would using the median result be more appropriate? [1]
Better to use median when have a skewed distribution, can avoid the influence of outliers
When would you use IQR vs STD? [1]
When wide outliers / skewed distribution: Better to use IQR in this case, to avoid the influence of outliers
What value is changing between the different colours in this Gaussain Distribution?
mean value
What value is changing between the different colours in this Gaussain Distribution?
Standard deviation
What is the standard deviation measuring? [1]
It is essentially calculating the average distance from the mean, and therefore the measure of spread of the results you have obtained. This is shown visually on the image here.
What are the references ranges are for 95%, 99% and 90% range for STD?
learn
What are the references ranges are for 95%, 99% and 90% range for STD?
learn
99% range (0.5th to 99.5th centile) = mean ± 2.58 SDs
95% range (2.5th to 97.5th centile) = mean ± 1.96 SDs
90% range (5th to 95th centile) = mean ± 1.64 SDs
Repeated sampling from a population
If the sample size isn’t too small then the distribution of the sample mean will be []
If the sample size isn’t too small then the distribution of the sample mean will be Gaussian
What is the STD of Gaussian distribution called? [1]
standard error
How do you calculate standard error of the mean? [1]
What would the standard error of the following be?
n=163
mean=22
standard deviation=4
How do you calculate the 95% confidence interval (CI) of a sample mean?
95% CI = sample mean ± 1.96 × standard error
key !!
What do the results from condfidence interval for the mean mean?
E.g. if 21.4-22.6
If results is 21.4 0 226:
We would expect 95% of samples of the same size to have a mean BMI between 21.4 and 22.6
95% confidence interval
Which is the correct definition?
In the population we are 95% sure that the mean weight could be as low as 75kg or as high as 81kg
In this study 95% of men weighed between 75kg and 81kg
Which is the correct definition?
In the population we are 95% sure that the mean weight could be as low as 75kg or as high as 81kg
In this study 95% of men weighed between 75kg and 81kg
What is the difference between reference range and CI? [1]
The reference range is defined as the interval between which 95% of values of a reference population fall into, in such a way that 2.5% will be below and 2.5% will be above.
Confidence interval is more concerned with the idea that the mean could be as low as/high as the two values given.
What is difference in values used to calculate STD and SE? [2]
Use standard deviation for ranges (for individual values)
Use standard error for confidence intervals (for means)
What is correlation (pearson) score for the following?
Perfect positive correlation: r=1
Perfect negative correlation r=-1
No correlation = r=0
If the data do not follow a Gaussian distribution or there is a non-linear monotonic relationship [] correlation can be used
If the data do not follow a Gaussian distribution or there is a non-linear monotonic relationship Spearman’s rank correlation can be used
x
Pearson’s correlation and linear regression describe which type of associations? [1]
Pearson’s correlation and linear regression only describe linear associations
Different regression curves can be fitted where the data pattern is
What type of regression modal would you use for the following?
Polynomial – quadratic (y=b0+b1x+b2x2)