S1 - Central Tendency and Spread

Question 1

What is the equation for mean?

Answer 1

∑x / n

Question 2

What is the equation for the mean from a frequency table or a grouped frequency table?

Answer 2

∑ ƒx / ∑ƒ

Question 3

What do you need to look for when working with grouped data?

Answer 3

Ensure that groups include all values (ie. 22 < x < 23 and 24 < x < 25 would need to be changed to 21.5 ≤ x < 23.5 and 23.5 ≤ x < 25.5)

Question 4

If data is grouped, what values should you use as the x (or list 1)?

Answer 4

Midpoints

Question 5

What is the interpolation equation?

Answer 5

Lower class boundary + ((ℎ𝑜𝑤 𝑓𝑎𝑟 𝑖𝑛𝑡𝑜 𝑡ℎ𝑒 𝑔𝑟𝑜𝑢𝑝 / 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 𝑜𝑓 𝑔𝑟𝑜𝑢𝑝)
× 𝑐𝑙𝑎𝑠𝑠 𝑤𝑖𝑑𝑡ℎ)

Question 6

What is σ?

Answer 6

Standard deviation

Question 7

What is the square root of variance?

Answer 7

Standard deviation

Question 8

What is σ²?

Answer 8

Variance

Question 9

What is the equation for σ?

Answer 9

Square root of Σx²/n - (Σx/n)²

Question 10

When using coding, what do you do to the mean?

Answer 10

Undo everything

Question 11

When doing coding, what do you do for standard deviation?

Answer 11

Only undo the multiplying and dividing of the equation, and ignore the add and subtract parts

Question 12

What comparisons do you need to include when comparing data sets?

Answer 12

• One about average
• One about measure of spread (s.d.)
• Give actual values and interpret in context of the question