Collecting and Interpreting Data Flashcards
simple random sampling
the items in the sample are chosen by a random process such as drawing from a box. Every member of the population has an equal chance of being selected
opportunity sampling
choosing individuals for a sample as opportunity arises such as interviewing passers - by
systematic sampling
selecting individuals from a population by a systematic method, such as selecting every 10th individual on a list of the population
stratified sampling
used when the population can be divided into subgroups using criteria such as age or gender and ensures all sub groups (strata) are represented in the sample
Quota sampling
Used when the population can be divided into strata . A certain number of items from each stratum are required
cluster sampling
when the population consists of subgroups which are each reasonably representative of the population for example year 6 classes in several schools.
The sample is taken from just a few of these subgroups
self selected sampling
when individuals choose to be part of a sample such as a survey on the internet
categorical data
not numerical in value
discrete data
numerical data that can take only specific values such as shoes size or number of pets
continuous data
numerical data that can take any real value in a range, such as weights or times
what type of data is bar charts used for
categorical data
what type of data are histograms used for
to illustrate grouped data
how to calculate frequency density
frequency / class width
positively skewed
right hand tail to the distribution. The median is closer to the lower quartile than to the upper quartile
negatively skewed
left hand tail to the distribution. Median is closer to the upper quartile than lower quartile
