 Hey guys, it's a room. Hope you found Biostats made easy part one useful and enjoyable in relation to sensitivity Specificity positive predictive value negative predictive value and prevalence. Let's get straight to the next part All right, something that we have to point out here is once we're here is check out sensitivity It's equal to one minus the false negative. All right, so what's important here is as your sensitivity is approaching 100% Okay, it means that this must be zero right for if your sensitivity is approaching 100% Then your false negative is zero if your false negative is zero that means all of your true negative is 100% and if your true percent if your true negative is 100% Because your false negative is zero because you're approaching 100% Then if your true negative is 100% negative you're confident that nobody else has it if everybody doesn't have it Then you're confident that nobody has it because that's a hundred percent true negative Therefore you can rule it out and that is why in first aid you see it as snout As far as specificity is concerned your specificity is Equal to one minus your false positive. Okay, so that means obviously as your specificity is approaching 100% Right your specificity is approaching 100% that means your false positive must be zero and if your false positive is zero It means it's 100% true positive What does that mean if a hundred percent of the people have it then you can rule it in and therefore that's why you get Spin on your first aid acronym. All right, so let's work out a problem So what you can see the practical application whenever you see this on any practice question go ahead and put There's your reality plus minus plus minus. This is your man-made test true positive True negative your plus and the minus or opposite faults go by the test false positive And then your plus and your minus or faults and then go by the test your false negative sensitivity go by alphabetical order sensitivity and Specificity all right, so let's give some values here Let's say that this is 20 and it and remember when the question actually comes They're not going to actually label this for you But what they will do is they'll give you the numbers So these are your numbers 20 80 10 and 90 and now they're asking you sensitivity when you see Sensitivity remember everything has the truths on top. All right, so you see sensitivity. There's your true You come straight down so it's 20 divided by well, it's your true positive divided by a true positive Plus false negative. So it's your 20 divided by your 20 plus your 80 is a hundred and therefore it is equal to 0.2 Your specificity. All right, remember your truths go on top like we talked about every time the truth go on top So then it's your true negative divided by your true negative plus false positive go straight up So then it's 90 divided by your 90 plus 10. It's a hundred. It's equal to zero point nine is your specificity Alright, so now let's say you wanted to see positive predictive value. Remember positive predictive value You're calculating how effective the test is go straight horizontal and remember the truths are always on top So true positive divided by true positive plus false positive 20 divided by 20 plus 10 30 Equals 0.66. All right, so then you go to your you go to your negative predictive value And what is negative predictive value again? You start with the truth so true negative divided by true negative plus false negative goes straight across horizontal your 90 divided by 90 plus 80 is 170 and Obviously if that's a decimal place, that's about 53. So 0.53 So that is your sensitivity coming straight down start with the truth your specificity going straight up start with your true Then your positive predictive value start with the truth straight across negative predictive value start with the truth straight horizontal this way Also, if you want to learn more about our courses and our tutoring be sure to take advantage of our promo code below And we can't wait to help you pass your test