Science - Non-science Flashcards
Uncertainty
A margin around a measured value which all other repeated measurement should fall around and is a measure of precision
Measurement Uncertainty
The margin for how close either side a marked measurement is to its actual value
- for analogy instruments it is half the smallest scale
- for digital instruments it is 1 unit in the least significant digit
Uncertainty in the mean
How close the average of the data scores collected are to the true value and is a measure of the random errors or precision
- Max value - min value/2
- Recorded to 1 sig fig
- Between measurement uncertainty and UITM choose the biggest ne
Absolute uncertainty
The measure of uncertainty in units as a independent value from the true value
Relative Uncertainty
The measure of uncertainty as a percentage of the true value
- Absolute uncertainty/measured value * 100
Error
The difference between the measured value and the actual value and is a measure of accuracy
Adding and subtracting uncertainty
Always ADD the ABSOLUTE uncertainties
Multiplying and Dividing Uncertainty
Always ADD the RELATIVE uncertainties
Random Error
Errors that are spontaneous and chance events that cause the measured values to be deviate randomly from the true value and is caused by human error or changing external conditions.
Measure of precision
Systematic error
Errors that occur repeatedly in the same spot and are to do with the measurement device or methodology or external conditions
Measure of accuracy
Reliability
Reliability is how trustworthy a value is as a result of its precision or proximity to other values
Validity
Validity is how trustworthy a value is as a result of its accuracy of its proximity to the true value and to the extent of which it measures what was intended.
Accuracy
How close a measured value is to the true value
Precision
How close a measured value is to other repeated measured values
Vernier callipers
A measuring device with two scales that measures the dimensions of objects
- To find measurement take the the the increment on the large scale just before the 0 of the small scale
- find the number of increments on the small scale that it takes to line up the large scale
- the first measurement plus the second is the actual measurement
SI Units
Standardized units for each type of measurement
- Distance: m
- Mass: Kg
- Time: s
- Electric current: A (Ampere)
- Temperature: K (Kelvin)
- Amount of Substance: mol
- Luminous Intensity: cd (candela)
Significant figures
Essentially the number of numbers in a measurement and how many shows precision of measurement
- the last digit is an estimate
- the more sig fig - the more precise
Sig Fig Rules
- Non - zero figures are always significant
- 12 and 18.98
- All FINAL zeros AFTER decimal point are significant
- 19.0 and 267.907 - Zeros between two other significant figures are significant
- 109 and 10.05 - Zeros used for spacing significant numbers from either side of the decimal point are insignificant
- 0.00004 and 129 000 - Always put a zero before decimal if no other sig figs
- 0.09 and 0.78
Calculating with Sig figs
If adding or subtracting, the number is rounded to the least amount of DECIMAL PLACES that were in the two numbers
- 12.23 + 3.6 = 15.8
If Multiply or dividing, the number is rounded to the number of SIG FIGS that were in the least precise number (one with least sig figs)
- 4.05 * 10 = 40
Absolute error
Measured value - accepted value
Relative error
Absolute error/accepted value * 100
Absolute variation
Measured value - Accapted value
Relative Variation
Absolute variation/ Average of measured and accepted value * 100
Variation
A deviation of the measured value from the accepted value, but it is not know that the are the same substance that is being tested for.
Measurement
It the best estimate + or - the absolute uncertainty. Basically communicated that it lies closest to the estimate could could be anywhere in that range.
Graphing
Used to convey relationships between things
Conventions:
- Error bars - use the highest uncertainty for each value and do vertical and horizontal
- line of best fit
- Compare systematic and random errors
- Display the equation of the line - y = mx +c
- Display R2 value
- Draw Min and Max lines
- Analyse the Uncertainty in the slope
- Analyse the Uncertainty in the c intercept
R2 Value
Shows how close the values are to the line of best fit, thus showing the precision
- the closer to 1, the closer the fit
Min and Max lines
Lines with the smallest gradient and largest gradient connecting the first and last error boxes.
Uncertainty in the slope
Max Gradient - Min Gradient / 2
Uncertainty in the y intercept
Max y-intercept -min y-intercept / 2
Modifications
Modifications can be made to experiments to increase their precision and accuracy. the 3 types are:
1. Refine - the elimination or systematic and random error and reduction
2. Redirect - Test different subjects are variables relating to the experiment
3. Extend - test for more variables or at more increments
Mistake
Not scientific, but refers to doing something inaccurate but with knowledge of how to do it accurately though carelessness
If a mistake is made - repeat the trial
Limitations
Characteristics of the methodology that hinder the collection and interpretation of data
Error vs Uncertainty
Systematic error dictates ACCURACY
Random error and uncertainty dictates PRECISION
Reliability vs Validity
Reliability is dictated by PRECISION
Validity is dictated by ACCURACY
Trends
The general direction of change in a variable
Patterns
Data that repeats in a predictable way
Relationships
Two or more data that is interdependent upon the other in direct or inverse proportion
