SI Units and Prefixes

• What are control variables? The variables that are kept constant thorughout an experiment
• What are independent variables? Variables that are changed throughout an experiment by you
• What are dependent variables? Variables that you measure in an experiment
• What is discrete data? Discrete data is numerical data that can only take certain values and is achieved from counting
• What is categoric data? Categorical data is a collection of information that is divided into groups.
• How are data sets that are categoric represented? Pie charts or bar charts
• What is continuous data? Continuous data is data that can take any value. Height, weight, temperature and length are all examples of continuous data.
• Examples of discrete data Shoe size, age, population
• What is ordinal data? Ordinal data is a kind of categorical data with a set order or scale to it.
• What is a random error? A random error is an error caused by uncontrollable factors such as enviromental conditions
• How would you reduce the effects of a random error in an experiment? - Repeat measurements several times - Calculate an average/mean
• What is a zero error? An error caused by an instrumement giving a reading when the true reading is zero
• How can zero errors be prevented? Calibrating instruments
• What is a systematic error? A repeatable error due to the equipment, method or techniqe being incorrect
• What does valid mean? A result that is reasonable, obtained from an acceptable method
• What does accuracy mean? How close a result is to the true value
• What does resolution mean? The smallest measurement on an instrument that can be read
• What does reproducibility mean? Similar results obtained by different investigators with different equipment
• What does repeatability mean? A result that can be achived multiple times when carried out under the same conditions
• What is an uncertainty? An estimate of the difference between a measurement reading and its true value
• What does precise mean? Measurements that are very close to each other
• Accuracy vs Precision diagram
• The smaller the amount of spread that your data has from the mean, the more _____ it is precise
• What is absolute uncertainty? The unceratinty of a measurement given as a certain fixed quantity
• What is percentage uncertainty? Where uncertainty is given as a percentage of the measurement
• What is fractional uncertainty? Where uncertainty is given as a fraction of the measurement
• Formula for percentage uncertainty
• Formula for fractional uncertainty
• Uncertainty symbol
• What do you do with the absolute uncertainties when adding/subtracting data? Add the uncertainty
• What should you do to the uncertainty of a variable when it is being raised to a power in the formula? Multiply the percentage uncertainty by the power
• When you are multiplying or dividing data, what should you do with the uncertainties? You must add the percentage uncertainties
• State a cause of parallax error Reading a scale at a different angle each time, due to not taking the reading at eye level
• Is electronic noise in the circuit of an ammeter random or systematic error? Random error as it will cause fluctuations in readings and cannot be removed
• How can percentage/fractional uncertainties be reduced? Measure larger quantites e.g a longer rope will have a smaller percentage uncertainty than a shorter one
• What is the difference between a reading and a measurement? A reading is when one value is found a measurement is when the difference between two readings are found
• What is the uncertainty equal to? (relative to resolution) Half the resolution (also known as smallest division)
• How many significant figures should the uncertainty be? The uncertainty should be to the same number of significant figures as the data
• Why does repeat readings provide more accurate data? Calculate a mean Remove anomalies
• What do we call an error that does not follow a pattern? Random