Data Analysis Skills (U1) Flashcards
There is ——— in all measurements. (Fill in the blank)
- Uncertainty
How do you recognise uncertainty?
- The instrument used for the measurement
- The procedure making the measurement ( human factor)
- The environment in which the measurement is being taken
Define Accuracy?
Compares a measurement to the true value.
Define Precision?
Describe how closely measurements are to each other and how carefully measurements were made.
Define uncertainty?
The inability to actually measure a true value and the subsequent doubt created about data.
Define error?
The difference between the true value and the measurement and can’t be eliminated because of many different reasons.
What are the two basic types of error?
1) Systematic errors
2) Random errors
What is a systematic error?
Errors that affect the accuracy of a measurement.
What can systematic errors cause?
They cause readings to differ from the true value by a consistent amount each time a measurement is taken.
How do instruments come into systematic errors?
e.g. The instrument has not been calibrated properly, so the errors are consistent.
What is a random error?
Errors that effect the precision of a measurement and are always present in measurements.
What can cause random errors?
These errors are unpredictable variations in the measurement process.
What causes random errors?
e.g. estimating when measuring between increments on an instrument, sampling like sample size, and spread, parallax error , instrument sensitivity eg measuring with a metal ruler on a hot day
How can you reduce random errors?
Using an average measurement from a set of measurements, or
Increasing sample size.
How do you calculate uncertainty using analogue equipment?
1) Find the smallest increment of measurement
2) Divide by two
3) Round to 2 decimal places
How do you calculate uncertainty using digital equipment?
The uncertainty is part of the smallest reading.
e.g. (0.1g), (0.05g)
How do you calculate relative uncertainty?
Relative uncertainty =
+_ (Absolute un/ measurement) x 100
What does relative uncertainty tell us?
The % uncertainty range.
How do you calculate the uncertainty of an average?
= +_ (max - min/ 2)
What is the Mode?
The value that appears most often in a set of data.
What is the Range?
The difference between the lowest value and the highest value.
What is the Median?
The middle number in a list of numbers ordered from lowest to highest
What is the Mean?
The total of all the values, divided by the amount of values (The average).
What is the formula to calculate the mean?
Mean= Sum of values/ Number of values
What is the standard deviation?
The measure of precision ( how much the data differs from the mean). Specifically, it shows you how much your data is spread out around the mean or average.
What is the standard error?
This is a measure of accuracy rather than precision and thankfully a calculation we can do with excel, meaning you will not have to do this calculation by hand.
What is an outliner in statistics?
Is a data point that differs significantly from other observations.
