Accuracy Definition and 236 Threads

Hi everone, Really stuck on this one, if anyone has any suggestions I would be more than greatful! Problem: A HIV test detects at 90% accuracy It falsly detects people as positive without HIV at 2% and it is estimated that 50% of the tested patients have HIV I need to work out the...

Ok. I'm fairly new so go easy on me. I apologise if this is posted in the wrong section. Can someone point me in the right direction of being able to work out samples of a web poll. A web poll I did returned the following results for a sample of 40 people and spending habits of a...

Hi. I was wondering if it's possible to calculate bullet accuracy in terms of percentage in a series of ranges, given bullet's max effective range, a series of ranges, bullet mass and velocity with gravity (assuming no wind resistance, or any frictional resistance). I'm looking for a...

Homework Statement The planned Gaia satellite is a successor to Hipparcos. It will have an astrometric accuracy of 24 micro-arcseconds, and be able to detect Cepheid variable stars in the Magellanic clouds (~ 70kpc away). Estimate how accurately Gaia will determine distances to these...

I've got nine sets of data (three people each took ten measurements of three different distances), and I need to find an estimate of the accuracy to which each person measured each distance. I've already calculated the mean and standard deviation for each set of data, but I don't know how to...

Hello everyone--first post--thank you for having me this seems like an awesome place :biggrin: I'm not totally sure where to post this since it's a general problem solving question but basically I want to be able to solve physics and math problems in a shorter period of time. Aside from the...

We did an experiment with abysmal accuracy. I'm now writing up my report and would like to meaningfully express the error between calculated and measured values. EXAMPLE calculated T=0.284 measured T = 0.201 I want to express the difference between them as follows: % difference...

Hi, I have a function f(x) = \frac{\cos(x^2)+x}{x^2+2},\quad x\in[0,3] I have to find the extreme values of the function in in the range [0,3], with Maple, by solving f'(x) = 0. Maple will solve these numerical, and I get 3 values. c_1 = 0.5345058769, c_2=1.732313261 and c_3=2.461303848 ...

Hi all, I was rather hopeing that someone here may know of a way to accurately measure the frequency of a sound wave? The reason I need to be able to do this is to investigate the doppler effect. I am able to measure the start frequency accurately using the following piece of software...

Hello, I'm trying to decide how I will provide excitation voltage to the wheatstone bridge of a load cell. The output of the load cell will be amplified by an LT1167 In-Amp. How concerned should I be about the precision/accuracy of the excitation voltage? Since the In-Amp will reject common...

I have a few questions regarding measuring devices in systems such as ventilation, heating, cooling etc. When calibrating these I come across the terms "accuracy" and "resolution" (directly translated from norwegian). I a bit confused about the difference of these. Can someone explain this to me...?

Hi, What exactly is the difference between accuracy and sensitivity as regards experimental apparatus? Thanks. :smile:

Hey, I have just finished running all the regressions for my thesis and I now have a nice 8-variable regression with an r² if 0.53. Almost all my hypothezised variables are significant. I am now wodering if there is a possibility to somehow test the forecasting accuracy of this model? I am using...

Does anyone know what is the most accurate reading of SR's time dilation or space contraction? I.e. has anyone been able to verify the accuracy of SR to 10^-15?

I am verifying and validating a rotational state propagator used in a dynamic simulation package. I have found some problems and solutions to them. This post outlines the propagation, the problems, and the solutions. Some questions before I start: - Has anyone else analyzed stability and...

my question is about the availability of present technology is it possible to screw a nut & bolt very ,very pricisely in space. each of them will be of 10000kg and about 0.7km most important-they will be rotating at a speed of 0.5 RPM

What is the difference between accuracy and precision?

hi all, can someone explain to me if i were to theoretically calculate current using an ammeter in small units eg micro amp's 10^-6 and physically use an ammeter to obtain results why do they differ greatly? and also when i am using a cathode ray oscilloscope (CRO), when i am measuring...

The following question appeared on one of my exam papers. A CCD of pixel density 10Mpixel (1cm^-2) is used to image a component of length 10cm. Show how this does or does not meet the required accuracies of +/- 0.025mm. A similar question was asked in a previous exam where the...

What is the accuracy of this statement? "Something strange is going on in physics, something so strange, in fact, that some people who've bothered ot think about the strangenoess now declare that physics is looking more and more like Eastern mysticism. This weirdness is taking place in the...

I NOTICED THAT THE TIME REQUIRED FOR A GIVEN MASS OF A LIQUID IS PROPORTIONAL DIRECTLY TO THE MASS OF THE LIQUID PROVIDED THE HEAT SUPPLY IS CONSTANT,WHICH MAKES t PROPORTIONAL TO m,the heat is constant.now heat is mctheta +ml.which makes t =m^2(l+ctheta).how true is this,is there a fault i...

I've been trying to figure out how to calculate the exact area of a ruled surface. I think I've come to a solution that works, but I'm not sure it's totally accurate. The procedure is as follows: Consider two curves. A ruled surface is constructed by connecting each point on one curve to a...

Suppose f(x) =x^{1/4} . If x is accurate to within 6%, within what percent is f(x) accurate ? i know that %percent error = delta F/ f(x) = f'(x)*deltaX / f(x) what i don't know is how to get delta f out this this information

How would I find the sensitivity and accuracy of electronic weighing scales?

I just want to check if I got this right. Given this graph, I need to define a step function: | ---------| C | _________|_______________ | -C |_________ | So, my definition is: C[-u(t) + u(-t)]. Thanks for checking this.

For instance, will attempts to predict comprehensively eventually prove contradictory?

Hi As the title says i am trying to find a good example (easy diffrential equation) to demonstrate Euler's method to explain it easily without a lot of calculations, help is appriciated

I don't really know where this thread belongs. I trust the mentor to move it, if necessary. How do mood rings work? How accurate are they? As always, any and all relevant information is appreciated.

It seems to me that I've got part (a) right, but I'm not so sure about what I have in part (b). I just need to know whether or not I am on the right direction. Any help is highly appreciated. :smile: Problem The force due to gravity on an object with mass m at a height h above the surface...

For a physichs project I had to build a trebuchet. I measured how for it shot, and how long it took. After some calculations I got: Vi in the X= 6.258 VI in the y= 6.64 Accel in X= 0 Accel in Y= -9.8 Distance in the X= 4.8 Distance in the Y= 2.25 Time in the X= 1.36 Time In the Y= .68...

Hi, Suppose i fit some data with a curve, using Levenberg-Marquardt (or equivalent). How do I estimate the accuracy of the parameters (by this i mean p plus or minus something). I've read somewhere that its done using the jacobian and covariance matricies I think, but not sure. Anyone know if...

If you were to create a seemingly perfect circle on your computer and then zoom in on it, wouldn't it have line segments rather than all curves? Of course, with the computer it is a matter of pixels. But what about in real life?

My dad and I got in an argument about accuracy of pi values. He said that the ratio 22/7 will always be more accurate than any decimal value of pi. I said that the value 3.14159265358979 is much more accurate. I'm 100% certain that I am correct, but I can't really think of how to prove this...

No, I'm not talking about courting strategies , I'm talking about the methods by which geologists date rocks and paleontologists date fossils. First off, I'd like to know what the different methods are. But, more importantly, I'd like to know how accurate they are...what is the margin of...

This thread has two purposes: 1) Can anyone tell me of a site (or sites) that deal with the accuracy of the science in modern movies? 2) If anyone would like to discuss, take apart, or ask questions about the science of any movie, they may do that here. As always, any and all...

For exmaple you can represent one third more accurately with fractions (1/3) than with decimals (.33 etc etc). So why do we use the decimal system ?