The key ingredients to confidence intervals are outlined as well as their interpretation as a indicator to the level of uncertainty attached to a point estimate. A generic template is offered which can subsequently be applied to the various scenarios encountered in Statistics 1. Duration: 11 minutes 50 seconds.
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Video tutorial 6.2 Review of confidence interval scenarios: single parameters
Building on the generic template given in Video tutorial 6.1, the different scenarios of single point estimates which appear in the Statistics 1 subject guide are reviewed. These comprise confidence intervals estimating a single population mean, μ, and a single population proportion, π. For the former case involving means, consideration must be given to whether the population variance, σ 2, can be assumed to be known and, if not, the mechanism for dealing with this is discussed. Duration: 15 minutes 26 seconds.
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Video tutorial 6.3 Review of confidence interval scenarios: differences between two parameters
This Video tutorial extends Recording 6.2 to consider constructing confidence intervals for differences between two population means, μ1 - μ2, and the difference between population proportions, π1 - π2. Again for the mean case, attention must be paid to whether the two population variances, σ21 and σ22 respectively, are known. If unknown, estimating the variances individually and producing a pooled estimate are considered. Duration: 19 minutes 27 seconds.
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Video tutorial 6.4 Computing minimum sample size to achieve a given confidence interval width
Question: James thought the population proportion of the electorate who intended to vote for the incumbent government in the forthcoming election was 34%. To investigate this hunch he decides to estimate this with a sample proportion. He sets a tolerance limit of 0.10 with 90% confidence. What is the minimum sample size required? Duration: 11 minutes 12 seconds.
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Video tutorial 6.5 Confidence interval for the difference in proportions
Question: A researcher was investigating computer usage among students at a particular university. 200 undergraduates and 100 postgraduates were chosen at random and asked if they owned a laptop. It was found that 81 of the undergraduates and 63 of the postgraduates did. Find a 95% confidence interval for the difference in the proportion of undergraduates and postgraduates who own a laptop. Duration: 9 minutes 34 seconds.
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Video tutorial 6.6 Confidence interval for a population mean, variance unknown
Question: A random sample of 8 students was taken and their scores in a statistics paper recorded. The sample mean was calculated to be 
= 71.2$ and the sample variance, s2, was 4.9. Compute a 99% confidence interval for the mean statistics score for all students taking the course. How can the interval width be made narrower? Why? Duration: 11 minutes 34 seconds.
= 71.2$ and the sample variance, s2, was 4.9. Compute a 99% confidence interval for the mean statistics score for all students taking the course. How can the interval width be made narrower? Why? Duration: 11 minutes 34 seconds.Click HERE
Video tutorial 6.7 Confidence interval for the difference in population means, variances unknown
Random samples are taken from two populations with distribution N(μX,σ2) and $N(μY, σ2) (i.e. their variances are the same). The summary statistics for the two samples are as follows:
| Sample size, n | Sample mean, m | Sample Variance s2 | |
| x-data | 19 | 7.0 | 1.69 |
| y-data | 25 | 5.1 | 2.56 |
Compute a 95% confidence interval for the difference μX - μY between the two population means. Duration: 13 minutes 5 seconds.
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