Flashcards in Statistics - AS Deck (31)
What is a population?
is the whole set of items that are of interest.
What does a census do?
Observes or measures every number of a population.
What is a sample?
Is a selection of observations taken from a subset to find out information about the population as a whole.
What is a simple random sample?
of size n is one where every sample of size n has an equal chance of being selected.
What is systematic sampling?
the required elements are chosen at regular intervals from an ordered list.
What is stratified sampling?
the population is divided into mutually exclusive strata & a random sample is taken from each.
What is the equation for sampled in a stratum?
(no. in stratum/no. in population) * overall sample size
What is quota sampling?
an interviewer or researcher selects a sample that reflects the characteristics of the whole population.
What is opportunity sampling?
consists of taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking for.
What is quantitative data/variables?
Data/variables associated with numerical observations.
What is qualitative data/variables?
Data/variables associated with non-numerical observations.
What is a continuous variable?
a variable that can take any value in a given range.
What is a discrete variable?
a variable that can take only specific values in a given range.
What are classes?
data presented in a grouped frequency table, the specific data values are not shown.
What are the class boundaries?
The max & min values in each class.
What is the midpoint of a class?
the middle value of the class boundaries.
What is the class width?
the difference between the upper & lower class boundaries.
What is the daily mean temperature - large data set?
this is the average of the hourly temp readings during a 24hr period.
What is the daily total precipitation - large data set?
The total amount of precipitation recorded in a 24hr period.
What is the daily total sunshine - large data set?
recorded to the nearest tenth of an hour.
What is the daily mean wind direction & speed - large data set?
Mean wind direction are given as bearings & as compass directions.
The data for wind speed is categorised according to the Beaufort scale.
What is Beauforts scale?
is an empirical measure that relates wind speed to observed conditions at sea or on land.
What is the daily maximum gust?
this is the highest instantaneous windspeed recorded. The direction from which the maximum gust was blowing is already recorded.
What is the daily maximum relative humidity?
given as a percentage of air saturation with water vapour. Relative humidities above 95% give rise to misty & foggy conditions.
What is the daily mean cloud cover?
measured in ‘oktas’ or eighths of the sky covered by cloud.
What is the mean visibility measured in decametres (Dm)?
This is the greatest horizontal distance at which an object can be seen in daylight.
What is the mean pressure?
measured in hectopascals (hPa)
What is the null hypothesis h0?
Is the hypothesis that you assume to be correct.
What is the alternative hypothesis H1?
Tells you about the parameter if your assumption is shown to be wrong.