In this blog I cover Hypothesis Testing, I have tried to explain it in a simple way, also I have given couple of scenarios where we need to build hypothesis testing.

Hypothesis Testing:

What is a Hypothesis ? : In statistics a hypothesis is a premise or a claim that we want to test or to investigate.

So how do we test or investigate ?

We do a survey, get a sample data, and we use that sample data to test the claim.

What is a Null Hypothesis ?

Null Hypothesis means the default hypothesis, i.e the thing that is kind of a established.

It is denoted as Ho.

Ho : Currently accepted value for a parameter

When we are looking at a parameter of population, we have a currently established thing,

may be a mean value of IQ or something based on previous study

What is Alternate Hypothesis ?
Alternative Hypothesis: also called as research hypothesis and is denote as Ha

Ha : It involves the claim to be tested.

Eg. Suppose it is believed that a candy machine makes chocolate bars that are on average 5g.

A worker claims that a machine after maintenance no longer makes 5g bars.


Null Hypothesis Ho : mu = 5g

Alternate Hypothesis Ha : mu <> 5g

Null hypothesis and Alternate hypothesis are mathematical opposites

Possible outcomes of this test :

1. Either reject Ho in favour of alternate hypothesis

2. OR fail to reject Ho

Test Statistic: Calculated for sample data .

Level of Confidence : How confident are we in our decision (usually taken as 95%)

Level of significance : Alpha = 1 – Level of confidence = 1-0.95 = 0.05

Ex –

A company states that they make soda straws of 4 mm diameter.

A worker believes that machine no longer makes straws of this size, he samples 100 straws

to perform hypothesis test with 99% confidence

Ho : average straw diameter = 4 mm

Ha : average straw diameter <> 4 mm


Doctor believe that avg teen sleeps on an avg. no longer than 10 h per day.

A researcher believes that teens on avg. sleep longer

Ho: average sleep hours of a teenager <= 10

Ha: avg. sleep hours of a teenager > 10


School board claims that atleast 60% of students bring mobile ph to a school

A teacher believes that this no. is too high and randomly selects 30 students to test

at a level of significance of 0.02.

Ho : p >= 0.60 [ where p proportion of students bringing mobile ]

Ha : p < 0.60

confidence level = 1-0.02 = 0.98 ~ 98%

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