Other factors will include the accuracy of the measurements in a survey. Typically, larger surveys will produce estimates with smaller confidence intervals compared to smaller surveys. A wide confidence interval indicates that we are less sure and perhaps information needs to be collected from a larger number of people to increase our confidence.Ĭonfidence intervals are influenced by the number of people that are being surveyed. What factors influence a confidence interval?Ī narrow or small confidence interval indicates that if we were to ask the same question of a different sample, we are reasonably sure we would get a similar result. The significance level simply indicates how precise they are willing to be. However, researchers can calculate CIs at any level of significance, such as 90 per cent or 99 per cent. The 95 per cent confidence level is used most often in research it is a generally accepted standard. The researchers are confident that if other surveys had been done, then 95 per cent of the time - or 19 times out of 20 - the findings would fall in this range.
#Confidence interval examples in nursing plus#
It is the range from 47.6 to 56.4 per cent - that is, 52 per cent plus or minus 4.4 percentage points.
The "margin of error" represents the confidence interval.
The margin of error is plus or minus 4.4 percentage points, 19 times out of 20." Miller if the election had been held last week. An example from the Globe and Mail newspaper regarding the mayoral race in Toronto read, "52 per cent said they would have voted for Mr. We often see CIs in newspapers when the results of polls are released. The confidence interval represents the accuracy or precision of an estimate. The CI is a range of values, above and below a finding, in which the actual value is likely to fall. Each time you repeat the survey, you would likely get slightly different results.Ĭommonly, when researchers present this type of estimate, they will put a confidence interval (CI) around it. However, your finding may be different from the actual value if you had surveyed the whole population. To save time and money, you would probably survey a smaller group of Canadians. You could ask every Canadian about his or her vacation schedule to get the answer, but this would be expensive and time consuming. There data are below:Ĭompute a 95 percent confidence interval.Imagine that you are trying to find out how many Canadians have taken at least two weeks of vacation in the past year. The data was used to make inferences regarding the other students taking the course. There were 24 individuals in the one section of the course polled. All students anonymously submitted the number of hours on a 3 by 5 card. How do these students compare to the national sample?Ī sample of students from an introductory psychology class were polled regarding the number of hours they spent studying for the last exam. Compute a 99 percent confidence interval based on this sample's data. A sample of 30 students are tested (sample mean=58, Standard Error=3.2). A standardized test is used to assess students knowledge of world events (national reported mean=65, S=5). The are concerned that their students are uninformed in regards to new from other countries. What does this information tell you about a particular individual's (an Alzheimer's patient) stage IV sleep?Ī university wants to know more about the knowledge of students regarding international events. Compute a 95 percent confidence interval for this data. The sample produced a mean of 48 minutes (S=14 minutes) of stage IV sleep over a 24 hour period of time. Number of minutes spent is Stage IV sleep is recorded for sixty-one patients. It has been hypothesized that individuals sufferering from Alzheimer's Disease may spend less time per night in the deeper stages of sleep. A sample of Alzheimer's patients are tested to assess the amount of time in stage IV sleep.