Statistics review 2: samples and populations. Whitley E, Ball J - Crit Care (2002) Bottom Line: The previous review in this series introduced the notion of data description and outlined some of the more common summary measures used to describe a dataset.However, a dataset is typically only of interest for the information it provides regarding the population from which it was drawn.The present review focuses on estimation of population values from a sample. View Article: PubMed Central - PubMed Affiliation: Lecturer in Medical Statistics, University of Bristol, UK. editorial@ccforum.com ABSTRACTThe previous review in this series introduced the notion of data description and outlined some of the more common summary measures used to describe a dataset. However, a dataset is typically only of interest for the information it provides regarding the population from which it was drawn. The present review focuses on estimation of population values from a sample. Show MeSH MajorConfidence Intervals*Normal Distribution*Population Surveillance*MinorCritical CareHemoglobinsHumansReference Values © Copyright Policy Related In: Results  -  Collection getmorefigures.php?uid=PMC137296&req=5 .flowplayer { width: px; height: px; } Figure 8: The Normal and t (with 19 degrees of freedom) distributions. Mentions: The t-distribution is similar in shape to the Normal distribution, being symmetrical and unimodal, but is generally more spread out with longer tails. The exact shape depends on a quantity known as the 'degrees of freedom', which in this context is equal to the sample size minus 1. The t distribution for a sample size of 5 (degrees of freedom = 4) is shown in comparison to the Normal distribution in Fig. 7, in which the longer tails of the t-distribution are clearly shown. However, the t-distribution tends toward the Normal distribution (i.e. it becomes less spread out) as the degrees of freedom/sample size increase. Fig. 8 shows the t-distribution corresponding to a sample size of 20 (degrees of freedom = 19), and it can be seen that it is already very similar to the corresponding Normal curve.

Statistics review 2: samples and populations.

Whitley E, Ball J - Crit Care (2002)

Related In: Results  -  Collection

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getmorefigures.php?uid=PMC137296&req=5

Figure 8: The Normal and t (with 19 degrees of freedom) distributions.
Mentions: The t-distribution is similar in shape to the Normal distribution, being symmetrical and unimodal, but is generally more spread out with longer tails. The exact shape depends on a quantity known as the 'degrees of freedom', which in this context is equal to the sample size minus 1. The t distribution for a sample size of 5 (degrees of freedom = 4) is shown in comparison to the Normal distribution in Fig. 7, in which the longer tails of the t-distribution are clearly shown. However, the t-distribution tends toward the Normal distribution (i.e. it becomes less spread out) as the degrees of freedom/sample size increase. Fig. 8 shows the t-distribution corresponding to a sample size of 20 (degrees of freedom = 19), and it can be seen that it is already very similar to the corresponding Normal curve.

Bottom Line: The previous review in this series introduced the notion of data description and outlined some of the more common summary measures used to describe a dataset.However, a dataset is typically only of interest for the information it provides regarding the population from which it was drawn.The present review focuses on estimation of population values from a sample.

View Article: PubMed Central - PubMed

Affiliation: Lecturer in Medical Statistics, University of Bristol, UK. editorial@ccforum.com

ABSTRACT
The previous review in this series introduced the notion of data description and outlined some of the more common summary measures used to describe a dataset. However, a dataset is typically only of interest for the information it provides regarding the population from which it was drawn. The present review focuses on estimation of population values from a sample.

Show MeSH