Interpreting Data Flashcards
what is the median?
8,4,2,11,8,3,7
7
what is the mode?
8,4,2,11,8,3,7
8
what is the mean?
8,4,2,11,8,3,7
43/7 = 6.1
how do you calculate the standard deviation?
distance from the mean, squared
average squared distance from mean and then square root
what is the standard deviation?
8,4,2,11,8,3,7
3
how do you calculate the interquartile range?
25th to 75th centile
what is the interquartile range?
8,4,2,11,8,3,7
25th centile: 3
75th centile: 8
1, 2, 3, 4, 100
median or mean?
median
to avoid the influence of outliers
what is gaussian distribution and what is it determined by?
bell shaped curve/ normal distribution
the gaussian distribution is determined only by the mean and standard deviation
what happens to the gaussian distribution when there is an increase/ decrease in mean?
the curve shifts to the left if there is a decrease in mean
the curve shifts to the right if there is an increase in mean
what happens to the gaussian distribution when there is an increase/ decrease in standard deviation?
a decrease in standard deviation causes the curve to become narrow and taller
an increase in standard deviation causes the curve to become shorter and wider
what does 1 SD either side of the mean equal?
68%
the rest outlying equals to 16%
what does 1.64 SD either side of the mean equal to?
90%
the rest outlying equals to 5%
what does 1.96 SD either side of the mean equal to?
95%
the rest outlying equals 2.5%
How do you calculate the 95% range?
mean +/- 1.96 x standard deviation
How do you calculate the 90% range?
mean +/- 1.64 x standard deviation
How do you calculate the 99% range?
mean +/- 2.58 x standard deviation
what is the standard error?
this is the stander deviation of the means from all potential samples of the same size
how do you calculate the standard error?
standard deviation / square root of the sample size
what is the 95% confidence interval?
the 95% confidence interval of a sample mean contains the population mean with a probability of 95%
95% sure that the population mean is between that interval
how do you calculate the 95% confidence interval?
mean +/- 1.96 x standard error
what is the difference between standard deviation and standard error?
use standard deviation for the range
use standard error for confidence intervals
does an increase in sample size affect the range or confidence interval?
confidence interval
sample size is used to calculate the standard error
what does a correlation coefficient of 0 indicate?
there is no pattern
what does a correlation coefficient of 1 indicate?
straight line
what does a correlation coefficient of -1 indicate?
straight line
but for a high value for x there’s a low value for y (vice versa)
what is linear regression?
the linear regression line has an equation
y = a + bx
y os the outcome variable.
x is te predictor variable.
a is the y intercept.
b is how steep the slope is. change in y variable divided by change in x variable.
what is a p value for a result?
the probability of observing a result as or more extreme than the sample result if the underlying assumption in the population is true
what does a p value < 0.05 indicate?
statistical significane
probably not a chance effect
what a p value > 0.05 indicate?
not statistically significant
cannot rule out chance effect
when can p values be calculated?
when there is a comparison
comparing the means of 2 groups
association: are the observed results different from those expected
regression
what test uses p values?
chi-squared test
produce test statistics which can be interpreted using p-values.
what is the relationship between p values and confidence intervals?
they are consistent
if the 95% confidence interval for a difference in means does not include 0, then p<0.01
what test is used to compare the means?
two sample t-test
what does statistical significance mean?
the probability that an effect is not due to just chance alone
