Author information from the last article
Regionalt kunnskapssenter for barn og unge – psykisk helse og barnevern
Institutt for psykisk helse
NTNU
Forfatterbidrag: utforming/design av statistiske analyser, tolking av data, litteratursøk, revisjon av manus og godkjenning av innsendt manus.
Stian Lydersen er dr.ing. og professor i medisinsk statistikk ved Regionalt kunnskapssenter for barn og unge – psykisk helse og barnevern (RKBU Midt-Norge) ved Institutt for psykisk helse, NTNU.
Articles by Stian Lydersen
Percentages in rows or columns?
- Stian Lydersen
09.09.2024:
When reporting counts and comparing proportions, it can be useful to present the figures in a contingency table. But should the percentages be reported in the rows or the columns? To answer this question, we can ask ourselves what is exposure and what is outcome, and report percentages within each...
Machine learning in medical research
- Guro F. Giskeødegård,
- Stian Lydersen
29.05.2023:
Machine learning is used to find underlying patterns in data. This can be useful in medical research. Machine learning is a form of artificial intelligence that is used to find underlying patterns in data. It can be based on statistical methods, or other techniques from mathematics or informatics...
Do we need all the decimals?
- Stian Lydersen,
- Eva Skovlund
05.05.2023:
If we use too few decimal places, the result will be imprecisely reported. On the other hand, if we use too many decimals, we give the impression that the result is more precise than it really is. How many decimals to use should be a conscious choice. Using more decimals than necessary is not wrong...
Attrition analysis
- Stian Lydersen
24.10.2022:
Attrition will occur in most clinical studies. If those who drop out differ substantially from those who participate, the generalisability of the study's results may suffer. Attrition can occur because not all of the invited participants choose to take part in the study, or because some of the...
Measurements below the detection limit
- Guro F. Giskeødegård,
- Stian Lydersen
19.09.2022:
Many methods for measuring levels of a substance in a sample have a lower detection limit. Data from these measurements must be handled in a way that avoids systematic errors. Let's start with an example: Figure 1 shows a fictional dataset of measurements of serum levels of a substance in two...
Internal consistency: from alpha to omega?
- Kenneth Stensen,
- Stian Lydersen
29.08.2022:
Questionnaires often consist of scales composed of different questions and are intended to measure a given factor, for example anxiety or depression. Internal consistency is a measure of the strength of the relationship between questions in the same scale. When developing questionnaires and scales...
Logistic regression with more than two categories
- Stian Lydersen
23.06.2022:
When the outcome variable has only two levels or categories, standard binary logistic regression can be used. When it has three or more, we can use other variants of logistic regression. Let us start with an example: Munthe-Kaas et al. (1) studied a possible association between frailty before a...
Paired categorical data
- Stian Lydersen
19.05.2022:
To compare proportions in two independent groups, one can use, for example, Pearson's chi-squared test. However, if the data originate from matched pairs, we must use methods that account for the dependence within the pairs. Matched pairs can originate from various situations and trial designs. The...