2x2 Table False Positive False Negative True Positive True Negative for screening Tests
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- เผยแพร่เมื่อ 15 ต.ค. 2024
- http:__www.stomponstep1.com_2x2-table-false-positive-false-negative-true-positive-true-negative_
Laboratory test results are usually a numerical value, but these values are often converted into a binary system. For example, urine hCG Pregnancy Test test may give you values ranging from 0 to 30 mlU_mL, but the numerical continuum of values can be condensed in two main categories (positive and negative). We do this by setting a Cut-off Point. All measurements above this cut-off value are categorized as "positive" and all values below are "negative." If you change that cut-off point the positive vs. negative classifications (as well as TP, FP, TN, & FN) change. In everyday life, positive things are good and negative things are bad. But remember in most laboratory tests, a positive result means the patient has a disease.
A True result is a lab result that matches the truth or our best estimate of the truth based on the results of the best available test (called the Gold Standard Test). So a true result would be a positive HIV test in a person we know to clinically have HIV. A False measurement is obviously when the result does not match the truth. "Good" tests have mostly true measurements and few false measurements.
• True Positive (TP) = A diseased person who is correctly identified as having a disease by the test
• False Positive (FP) = A healthy person that is incorrectly identified as having the disease by the test
• True Negative (TN) = A healthy person who is correctly identified as healthy by the test
• False Negative (FN) = A diseased person who is incorrectly identified healthy by the test
Here is another way to think about these definitions:
• All with Disease = TP + FN
• All without Disease = TN + FP
• All that Tested Positive = TP + FP
• All that Tested Negative = TN + FN
Two-by-Two Tables
Questions involving TP, FP, TN, and FN will usually have a two-by-two table. Sometimes they will give you the actual table and other times they will give you all of the data for the table in sentence form and you have to make the table for yourself. You may have learned to refer to the boxes in a two-by-two table as A, B, C & D. I am going to strongly recommend you not do this. First off, those letter labels have no meaning. It is therefore more likely for you to get confused and make a dumb mistake. Additionally, the top left box in a two-by-two table may not always represent true positive. Sometimes, test writers will mix up the order of the columns and_or rows. I suggest using TP, TN, FP, and FN instead.
Sometimes they will give you an extra row and column that has totals. Don't let that throw you off. It is still a two-by-two table even though there are 3 columns and 3 rows. They just try to save you a step of calculation by giving you the row and column totals.
Now that you have finished this video on 2 by 2 tables you should check out the next video in the Biostatistics & Epidemiology section which covers Sensitivity, Specificity & Confirmatory Tests (www.stomponstep...)
If you liked this video and want me to make more please let me know by commenting, liking this video or by subscribing to my TH-cam channel. If you have a question, please don’t hesitate to ask and I’ll try to answer it ASAP.
Man, you are a damn saviour †. Have my dental epidemiology exam in a week and understood nothing. Thank you so much!
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Came across ur channel by a mistake but that was an awesome mistake. Subscribed right away and watch all the videos in one sitting...I feel so much better about biostats already. THANK YOU!
+Baby gal thanks for watching!
Thank you for loading up videos! I checked out ur website already...if u can do renal, pharm videos..that will be helpful..pleaseee.
You own. I'm sharing with my whole class. We have a biostats final exam tomorrow and this is going to be high yield for our exam as well as for the board exam.
+Nixi Cat Thank you so much for sharing. It really helps me out
Thank you for your simplicity. Why do professors make it seem so complex? Greatly appreciate how you "break-it-down". Keep doing what you're doing. (In biostatistics/epidemiology for FNP)
VeraNice Curls Thanks for the feedback!
this is very good. Thank you so much for doing these. These are a real help. Keep it up. I'm watching all of your stats videos today!!
nicole branch Thanks for the feedback!
Thanks a lot. Appreciate video simplicity and chart.
thanks for the simple explanation
+EpiStats: Epidemiology and Biostatistics thanks for watching!
thank you so much that was of great help for me i hope you contineous doing this
gud bless you
فدى عبدالله Thanks for the feedback! More videos to come soon
very helpful lecture and i really like it however i have a question will send in email.
So great! Thank you!
Remy Mercer-Slomoff thanks for the comment. Please tell your friends!
Excellent!
Thanks for the encouragement!
Thank you!
thanks alot
THANK YOU :)
nicole Meh No problem. I'm glad you found it to be helpful . Thanks for the comment!
Stomp On Step 1 my professors ALWAYS made this soooo complicated i am so impressed how u made it really really simple thx again
nicole Meh Thanks for the comment! I'm glad the video helped.
I like this video
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