2.1 Basic Stats - StudyNinja

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2.1 Basic Stats

These basic stats questions are asked in many different forms (Sample Data, Frequency table, Histogram etc.) which will be covered in each of the sub-sections of this section. However, at their core, all of these questions ask you something around basic statistics. Before learning about these different exam questions, it is important to develop at least basic understanding of these statistics. At the very least, following are the stats you need to understand:

Mean: This is the simplest of all to understand. Mean is the average value.

Median: Median is the middle value. So if you have height of 11 students in a class, you arrange them in ascending order then the median will be the 6th value. (5 heights lie below this value and 5 above).

Mode: Another simple stat to understand. Mode is the most occurring value in a data set.

Range: Difference between highest and lowest value in a data set.

Quartiles: Related to median, if you think median is the 50th percent (mid) value of the data set this can then be extended to calculate 25th percent value which is lower quartile or Q1 or 75th percent value or Q3. Q2 is the median itself if you are wondering.

Percentiles: Quartiles can be further generalized and you can calculate any percent value other the ones mentioned above and they are called percentiles.

Interquartile range: Difference between upper and lower quartile.

Standard deviation: On average how far apart are the values from the mean. Two data sets 10, 10, 100 and 40, 40, 40 have same mean of 40 but the first one has wider possibilities of values from 10 to 100; standard deviation captures this variation.

Once you are comfortable with the above you are ready to start with the real exam stuff. Scroll through each of the sub-sections below:

2.1.1 Sample Data

2.1.2 Frequency Table

2.1.3 Histogram

2.1.4 Dot-Plot

2.1.5 Stem-Leaf

2.1.6 Box-Whisker

There are broadly 4 types of questions you can expect in exam:

2.1.7 Exam Question Type 1

2.1.8 Exam Question Type 2

2.1.9 Exam Question Type 3

2.1.10 Exam Question Type 4

Study notes of this section and other resources can be accessed here:

– 2.1.11 Study Notes & Resources

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