STATS

• What is a census?

  • Measures every member of a population
  • Advantage: Accurate results
  • Disadvantage: Expensive and time-consuming
• What are sampling units?

  Individuals of the population that might be sampled.
• What is a sampling frame?

  A list of sampling units.
• What are the three types of random sampling?

  1. Simple random sampling
  2. Systematic sampling
  3. Stratified sampling
• What is simple random sampling?

  It gives every member of the population the same chance of being selected.
• How can you perform random sampling using a calculator?

  By using a random number generator.
• What is lottery sampling?

  It involves randomly picking names from a hat or bowl.
• What is an advantage of random sampling?

  It is bias-free because it is completely random.
• What is a disadvantage of random sampling?

  You need to have a sampling frame available.
• What is systematic sampling?

  It involves taking every kth unit from a population.
• How do you determine k in systematic sampling?

  By dividing the size of the population by the size of the sample.
• What is the starting point in systematic sampling?

  A random number between 1 and k.
• What is stratified sampling?

  It represents groups called strata within a population.
• How do you calculate the sample size in stratified sampling?

  By multiplying the sample size by the proportion of each strata.
• What is the advantage of stratified sampling?

  It reflects the population accurately.
• What is a disadvantage of stratified sampling?

  The population must be classified into strata, which may not be clear.
• What are the two types of non-random sampling?

  1. Quota sampling
  2. Opportunity sampling
• What is quota sampling?

  It fills strata by an interviewer or researcher instead of randomly.
• What is an advantage of quota sampling?

  You do not need a sampling frame.
• What is a disadvantage of quota sampling?

  It is not random, leading to potential bias.
• What is opportunity sampling?

  It involves selecting individuals who are available at the time.
• What is an advantage of opportunity sampling?

  It is easy and cheap to perform.
• What are the two types of data?

  1. Qualitative (non-numerical)
  2. Quantitative (numerical)
• What is a disadvantage of opportunity sampling?

  It is unlikely to be representative of the population.
• What is qualitative data?

  Data that is non-numerical, usually words or categories.
• What is quantitative data?

  Data that is numerical and can be either discrete or continuous.
• What is discrete quantitative data?

  Data that can take fixed values.
• What is continuous quantitative data?

  Data that can take any value in a particular range.
• What is the time frame for the large data set recorded?

  • Six months
  • From May to October
  • Years: 1987, 1990, 2015
• What are the three international weather stations mentioned?

  Perth, Beijing, and Jacksonville.
• Why is Perth unique among the international stations?

  Its summer and winter seasons are switched compared to the UK.
• What is unique about Beijing's climate?

  It has extreme seasonal variations with hot summers and very cold winters.
• What does "tr" mean in rainfall data?

  Trace, meaning less than 0.05 millimeters of rain.
• What does "n/a" mean in data readings?

  Not available, indicating the reading is not available.
• What does $\bar{x}$ represent in statistics?


  The mean of a data set.
• How do you find the position of the upper quartile (Q3) in listed data?

  By calculating $\frac{3n}{4}$.
• What is the formula for finding the upper quartile (Q3) in listed data?

  Q3 is found by taking three quarters of the way along, which is three times the number of pieces of data divided by four.
• How do you find the median in listed data?

  The median is found by dividing the number of pieces of data by two.
• What should you do if you get a decimal when finding quartile positions?

  You should round up to find the corresponding position.
• How do you find the cumulative frequency?

  You find cumulative frequency by adding the frequencies sequentially.