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F Lecky

Publications and source records attributed to F Lecky.

10 recordsLinked to original sources
PubMed2001

Article 5. An introduction to estimation--2: from z to t.

Provided the sample size is large enough (that is, n greater than 100), the z statistic can be used to determine the confidence interval estimation of the population mean even when the sigma is not known. In these cases the estimation of the standard error of the mean is used. The z statistic is also valid when determining the population's proportion based upon a large sample. However, when dealing with smaller samples, the z statistic is replaced by the t statistic. This makes it possible to estimate, in a population with an unknown standard deviation: The probability of getting a sample mean greater than or equal to a particular value The value of a sample mean with a particular probability of occurring The probability of getting a sample mean between two particular values The confidence interval for the estimation of the population mean can also be determined using the t statistic.

Bias↗
PubMed2000

Trends in trauma care in England and Wales 1989-97. UK Trauma Audit and Research Network.

BACKGROUND: In 1988, the Royal College of Surgeons reported major deficiencies in trauma care in UK hospitals. We investigated whether and how that care has changed in the last decade by use of data collected by the UK Trauma Audit and Research Network. METHODS: We analysed injury-severity, process, and outcome variables from 91602 patients' records on the database at the end of 1997, collected from 97 (49% of trauma-receiving) hospitals in England, Wales, and two in Ireland. We did longitudinal analyses of odds of death, process variables, and individual hospitals' performance. We took account of potential selection bias from missing data and recruitment of new hospitals. FINDINGS: The severity-adjusted odds of death after trauma declined gradually from 1989 (odds ratio 1997/1989 0.63 [95% CI [0.49-0.82]). In 1997, the reduction in odds of death was significant even after adjustment for missing data (ratio 1997/1989 0.72 [0.55-0.92]) and recruitment of new hospitals (0.64 [0.44-0.93]). There was significant variability in the proportion of survivors (adjusted for severity of injury and age) between the highest and lowest 10% of UK hospitals. The time between the call to the emergency services and arrival at hospital increased from 32 min in 1989 to 45 min in 1997, irrespective of injury severity. The proportion of severely injured patients seen first by senior doctors increased from 32% to 60%. INTERPRETATION: Hospital care has made a valuable but variable contribution to reductions in case fatality after injury in the UK in the past 10 years, though further improvement is possible.

Aged↗
PubMed2000

An introduction to everyday statistics--1.

Descriptive statistics are used to summarise numerical information so that it is in a more manageable form. There are a variety of ways of carrying this out depending upon what type of data we are dealing with. There is also a choice when presenting data. Graphical and tabular formats are possible but each have strengths and weaknesses. Selection therefore needs to take these into account along with the format of the presentation and the type of data.

Humans↗
PubMed2000

An introduction to statistical inference--3.

Statistics inference is used to make comments about a population based upon data from a sample. In a similar manner it can be applied to a population to make an estimate about a sample. It is commonly seen in medical publications when the null hypothesis is being tested. This calculates the probability (p value) of a type I error--that is, that a particular finding is attributable to chance. It is also important to be aware of the chances of a type II error--that is, accepting the null hypothesis when it does not apply. Sample size, point estimate and variability are common factors that will affect the chances of making these two types of errors. Interpreting results therefore needs to take these factors into account as well as the clinical relevance of the findings. Statistical significance does not necessarily mean clinical significance.

Emergency Service, Hospital↗