Measurement Errors Flashcards
What is a systematic error?
Your mistakes
Incorrect instrument calibration
Pipetting error
Changes in experimental condition
What is a random error?
Reading errors
Sampling errors
Intrinsic variability - esp in biology
What does the reading error tend to be?
+/- half of the smallest division
ie 23 +/- 0.5mm on a ruler
Reading error takes into account biological variability
True/false
False
How do you work out the standard error of a count?
Square root of the number found
What is a sample in biology?
Specimen
What is a sample in stats?
Subset of numbers/population to analyse defined by a statistical parameter
What is a statistical estimator?
Sample attribute used to estimate a population parameter
Which value is more appropriate for skewed distributions: median or mean?
Median
The median is not sensitive to outliers true/false
True
Which is more appropriate for normal distribution: mean or median?
Mean
Statistical tests on this are more powerful than non-parametric tests
What is the standard deviation?
Measure of a spread of data points
Standard deviation depends on sample size
True/false
False
Standard error can be improved by decreasing sample size
True/false
False
