Tag Archives: e-math formula sheet

E-Math: How to Use the Mean and Standard Deviation Formula (Plus: Calculator Shortcuts)

One of the first topics that many Secondary 4 E-Math students learnt is a statistics chapter known as Mean and Standard Deviation (SD for short).

The nice thing about this chapter is that the 2 most important formula are both available in the E-Math (subject code: 4016) formula sheet! No memorization required, just understanding of their usage.

In this post, I will illustrate 2 methods to get the answers for mean and SD for ungrouped data (refer to example). The 2 methods are manual and calculator.


Given 15, 6, 18, 9, 2 and 4, find the mean and standard deviation.


Mean and Standard Deviation Manual Working
Mean and Standard Deviation Manual Working

Calculator, Casio fx-85MS:

  1. Mode, 2(SD)
  2. Enter the data in this manner, 15, M+ follows by 6, M+...
  3. To get mean: Press 'Shift', 2, 1,=
  4. To get SD: Press 'Shift', 2, 2,=

Here are some additional information you can obtain using the calculator:

Mean - SD from Calculator
Mean - SD from Calculator

Answers obtained through both methods are the same. By knowing these 2 methods, you can use either to double check.

Sec 2 to Sec 3: How To Prepare Yourself For Elementary Math

I have earlier written an article on Sec 2 to Sec 3: How To Prepare Yourself For Additional Math

For those who aren't taking additional math, how can you prep yourself this holiday? (Note: I ain't telling you to burn your holidays mugging. Nope! But I mean to say have some work time and play time!)

I remember I was given quite a bit of holiday assignments during Nov/Dec holidays. Read in Facebook comments, this is still the ongoing trend in schools. Finish those work fast (No motivation? Get friends to complete the work together )and you can play for the rest of the days! Do not be like majority of the folks who wait till the end of the holidays, only to realize school is starting in a few days time that they start knowing that homework is due.

What I personally suggest for prep for Sec 3 Elementary Math is to ensure that your Sec 1&2 foundation topics are built upon on solid ground (These topics are tested in 'O' levels and every often schools do not have the time to revise thoroughly during term time)

Some of the foundation topics are listed below:

  • Making subject formula
  • Algebraic expansion rules
  • Algebraic factorization
  • Properties of Angles
  • Mensuration (New syllabus e-math has formula provided in exams)
  • Similarity & Congruency
  • Statistics (Mean, Median, Mode)
  • Equation of lines

These topics involve some fundamental applications which will be revisited again in Upper Sec.

Some of the Major Sec 3 Topics you would be expecting include:

  • Indices (*new)
  • Quadratic Equations (*new+very important)
  • Congruency and Similarity (*revision+application)
  • Graphs (*new+add on from Sec 1/2)
  • Properties of Circle(*new)
  • Trigonometry (*new+very important+high weightage in E-Math & A-Math)
  • Co-ordinate Geometry (requires basics from Equations of lines from Sec 2)
  • Arc Length & Sector Areas (used to be A-Math topic but included in E-Math now)
  • Quartiles & Percentiles (Statistics)
  • Matrices (*new)

(Those highlighted ones are the topics which are heavily weighted and you must pay more attention in following through. They are also fundamentals you would need in A-Math as well)

You may want to familizarize yourself with the 'O' level E-Math formula provided but in school tests and exams, some schools choose not to provide.

(Click on image for larger view or you may even want to print out a copy and stick on your desk for easy reference)