Algemeen notes
20 important questions on Algemeen notes
What are two important guidelines for presenting statistical results?
- Understandibility: Statistics should be reported in a form that is easily understood by most people.
- Interpretability: report the statistics in units or measure in plain language, or at leas in terms that require the least statistical knowledge of your audience.
- "Confidence" : report a confidence interval (most often 95% CI) to indicate the confidence you have in the reported statistic.
Confidence interval = a region generated by a procedure that, under repeated sampling, contains the true value of the parameter of interest with a specified probability.
On what does the width of the confidence interval dependent?
- The standard error of the parameters -> the larger the sample, the smaller the standard error.
- The level of confidence -> 95% confidence interval is wider than a 90% CI. A 100% is (-infinite, +infinite), contains all possible values of parameter and is not very informative
What is:
1. risk difference
2. relative difference
3. (odd ratio)
- The difference of two proportions
- the ratio of two proportions
Deal with categorical data, displayed in two-by-two contingency table containing counts per category.
- Higher grades + faster learning
- Never study anything twice
- 100% sure, 100% understanding
For my 1st exam I got a C. Then, I started looking for ways to learn better and I came across Study Smart. Since then I have scored a A+, A, A- and another A. I highly recommend it to everyone who wants to hear it. I am so happy with it!!
I was struggling to finish all my first-year subjects for 3 years. Then I discovered Study Smart, which helped me to finish all of them within 3 months.
Because of StudySmart, things are going well in many ways. Before, I always had study stress and no time for anything. Now I feel calm and confident (because of the program). I used to score a B, now I usually score an A or A+.
Hey Chris, I really want to thank you very much for developing the platform, I usually got around C for my exams, now I scored an A+, an A and a A- !!
Since using Study Smart, my average has increased significantly. I even completed a statistics course with a A+ while I'm bad at statistics. I took on extra courses this year, because of Study Smart. Thanks so much!
Ever since I started studying with StudySmart I passed all my exams !!! No more re-sits!! At first, I was happy with a pass and now I only get good grades. Many thanks!
I aced all the courses I studied with Study Smart. For law, I first scored a D, and now an A! I’m 100% sure that I’ll pass all the courses I study with Study Smart.
I always thought I studied well. My grades were fine. I could never have imagined that applying these study skills would have such a huge and direct impact on my grades, my speed and the pleasure I have in learning.
For the first time, I finally feel totally confident about the way I learn. I have the perfect overview and make great progress in terms of speed and the grades I get. Thanks, Chris!
I immediately started to enjoy learning again, and my grades soared. All of a sudden, everything went better. I highly recommend Study Smart to all students..
Being able to create my materials online made the process of studying so much smoother and quicker. I no longer have to spend a huge amount of my time on creating my summaries.
At first, my notes were a mess. Now I use Study Smart to take my notes in a perfectly structured way. It helps me to save a lot of time and do other things I enjoy.
Students that study with Study Smart get better grades. The system applies all the learning methods in such a way that both well-performing students and students who struggle perform much better.
Hi Chris, I would like to thank you very much. Last year I scored C on a course, and this year I got an A+ thanks to your method! Thank you very much!
The largest effect is that my child is more enthusiastic about school! Every parent wants their children to be happy at school, Study Smart made it happen.
In high school, I failed several exams, and that has really changed now. I actually needed this tool very much back then. Since I started studying with StudySmart, I haven't had any D's. My average score is now an A and those are results I would have never had in the past
With my old method, I passed only 3 out of 8 courses. Since I started taking my notes digitally in Study Smart, I have passed all my courses on the first try. For me, StudySmart takes away the stress of wondering if I will pass or not.
Thanks to StudySmart, I passed all my exams, and with better grades than before! On top of that, I have mastered a very good study method now, which I am confident will help me earn my degree.
Calculation:
- standard error
- adjusted confidence interval
onderste foto = adjusted confidence interval
Does not perform well when the sample size is small -> so better to do an Adjusted (wald's) confidence interval.
What does a 95% Confidence interval mean?
Cohen's w effect size index (Blz.31)
it reflects the differences between the observed frequencies in the cells of a contingency table and that expected under the null hypothesis. Can be calculated from observed and expected proportions (relative frequencies) in each cell or from the test statistics X^2
Anova + variance calculation
- Analysis the variance in a set of observations
- it assigns chunks of the total variance to the independent variables and their interaction in the general linear model in equation 4.1 blz. 41
- the remaining residual variance or error is not explained by the model's factors
- to calculate variance -> use the sum of squared errors, SS. So the sum of the squared differences between each individual measurement and the overal mean, X| (streep erboven).
Why use contrasts? (and not post-hoc test)
Degrees of freedom
- Main advantage contrast is based on all observations in the ANOVA.
- so you have more degrees of freedom (than in post hoc test were you can only compare two samples)
- more degrees of freedom means a larger effective sample size and hence higher statistical power
- So a planned comparison is hypothesis-driven and formulated a priori. Also, unlike a post-hoc test, a planned comparison has more power as it uses the entire data set instead of a subset
Why multiple linear regression? Blz. 52
e.g.
- What factors (predictors/independent variables) explain or account for the variation of the dependent variable -> could lead to identification of causal factors
- What effect does one independent factor has on the dependent factor when you correct for another independent variable?
- When I have some info of independent variables, can I then predict the dependent variable?
There are two different ways to construct a multiple linear regression model. Blz.59
Sequential regression -> decided by statistical software.
Sequential regression -> forward selection or backward elimination, determines the order in which predictors are removed or added from a model under construction.
RMSE (root mean square error). Blz. 61
- Is a measure of the average deviation or error of the data points (yi) from the values calculated from the regression model (Y^i)
- The smaller RMSE the better -> the smaller the difference between all measured values and their predicted or calculated values, the better the model fits the data.
What is the Parsimony principle? Blz.67
Statistical power or sensitivity
Smallest effect size of interest. Blz.79
Type-2 error - False negative blz.82
Type-1 error - Fals positive. blz. 82
Noncentrality parameter, ncp. blz.82
- Is a measure of how far the peak of the t-distribution under Ha has shifted from that under H0.
- the same effect size d wil five a larger ncp when sample size n increases.
- When Cohen's effect size d = 0 then ncp = 0 and we have a central t-distribution that is symmetric and centerend around 0.
How to increase the effect size d
- By decreasing variability (standard deviation)
- by increasing the smallest effect size of interest
The two consequences of two tailed testing are:
- There are now two critical t-values: one negative to the left of the central value t= 0 and one positive to the right. The H0 will be rejected when the significance test gives t > trite or t < -tcrit
- the crital t-values are more extreme as they have to enclose aress smaller than 5% under the distribution when H0 is true.
What is a post hoc test and when is it used?
The question on the page originate from the summary of the following study material:
- A unique study and practice tool
- Never study anything twice again
- Get the grades you hope for
- 100% sure, 100% understanding
