AplusA Stats App

CONFIDENCE INTERVAL CALCULATOR

Level of accuracy in percentages observed:

Confidence interval provides the level of accuracy of a given measure.

To conduct market research is to interview (or observe) a sample of individuals. The larger the sample, the greater the statistical accuracy.

For instance

Upon interviewing a sample of 500 GP’s, 20% are found to be using Product A. So, what is, within the total population, the actual proportion of users of Product A.

Assuming 5% risk level*, confidence interval is:

• 20% +/-3.5

• [16.5%-23.5%]

In other words, there is a 95% probability that the actual percentage of Product A users in the total population of GPs is between 16.5% and 23.5%.

COMPARING TWO PERCENTAGES

Statistical significance between 2 observed percentages:

Significance tests provide an indication whether observed percentages are significantly different or not.

Useful when comparing opinions (or attitudes) measured on two samples!

For instance

Upon interviewing a sample of 500 GP’s, 20% are found to be using Product A. Equally, upon interviewing a sample of 150 cardiologists, 25% of those are found to be using Product A. Would such a result suggest that a larger proportion of cardiologists is using Product A?

At 5% risk level*, the two percentages observed on these samples are not statistically different.

In other words, there is a 95% probability that the actual proportion of Product A users among GPs’ total population is similar to the actual proportion of Product A users among cardiologists’ total population.

SAMPLE SIZE CALCULATOR

Minimum sample size calculations:

This application calculates the minimum sample of respondents needed in order to achieve the required level of research accuracy.

By taking into account an expected percentage, as well as the corresponding confidence interval, it is possible to calculate the sample size needed for a given market research survey.

For instance

Research is needed to evaluate the level of use of Product A among anaesthetists. The desired confidence interval is +/-8. Approximately one third of anaesthetists is expected to be using Product A.

How many anaesthetists need to be interviewed in order to achieve this margin of error?

At 5% risk level*, for an expected percentage of 33%, with a confidence interval of +/-8, minimum sample size is 133 anesthetists.

In other words, if you interview a minimum of 133 anesthetists, there is a 95% chance to get a confidence interval of +/-8 if the proportion of Product A users in the anesthetist sample is 33%.

APLUSA STATS APP

The exclusive AplusA Stats Application!

3 most useful statistical tools in the palm of your hand (EN - FR)

CONFIDENCE INTERVAL CALCULATOR

For instance

COMPARING TWO PERCENTAGES

For instance

SAMPLE SIZE CALCULATOR

For instance

APLUSA STATS APP

The exclusive AplusA Stats Application!

3 most useful statistical tools in the palm of your hand (EN - FR)

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CONFIDENCE INTERVAL CALCULATOR

For instance

COMPARING TWO PERCENTAGES

For instance

SAMPLE SIZE CALCULATOR

For instance