I'm designing an experiment in which I want to have uneven allocations because one of the treatments is strongly suspected as being worse. This caused me to examine minimum detectable effects for a number of weeks and sample ratios. The test statistic is a mean.
For this I looped over this python function many times for different sample sizes and sample ratios:
statsmodels.stats.power.tt_ind_solve_power
The output looks like this:
https://preview.redd.it/nvw8qk7jad381.png?width=2150&format=png&auto=webp&s=eb88bde0aaa537e5dce4b6a7d72263e0d034f582
I must confess I was a bit shocked that the smallest MDEs weren't at 50:50 allocation and that it showed a sweet spot at around 30% allocation.
Is this correct or have I messed something up?
If this is correct, what's the explanation for it?
If this is the case, I'm surprised that I hadn't heard of this before as a means of increasing testing power.
Code:
https://preview.redd.it/v30tqsdmad381.png?width=1572&format=png&auto=webp&s=c10e5d0b6d89c06ecdf7bd884c9c166d57c2cbeb
import statsmodels.api as smimport csv
sample_sizes = [10000, 12000, 14000, 16000, 18000, 20000, 22000, 24000, 26000, 28000, 30000, 32000]
percenctages = [0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.49]
output = []for p in percenctages:for i, ss in enumerate(sample_sizes):n1 = (1-p)*ssn2 = p*ss# nobs2 = nobs1 * ratior = n2 / n1mde = sm.stats.tt_ind_solve_power(effect_size=None,nobs1=(1-r)*ss,alpha=0.05,power=0.8,ratio=r,alternative='smaller')output.append([i+1, p, mde])
with open("pre_test_paramaters.csv", "w", newline="") as f:writer = csv.writer(f)writer.writerows(output)
Corrected output:
https://preview.redd.it/39c6zrjbde381.png?width=2136&format=png&auto=webp&s=821175f7d89783f14e5eb979d3ebff22155ffbe7
I'm running AB-test with an Average Page Depth (Per Session) as a non-binary key metric and now I'm totally confused with the need to deal with choosing MDE and sample size.
Look, I understand all those things about level of significance and how to choose between parametric or non-parametric tests. I thought I understood statistics until I had to launch an AB-test by myself.
Some resources say "Step 1. Estimate the desired conversion rate lift". Well, I don't know which rate lift I want. 10%? Okay. 5%? Okay. 1%? Okay. 0.001%? Any improvement is okay as long as it is statistically significant (I mean, p-value is <5%).
My question is: why should I bother about sample size and MDE if my statistical test says everything I need with a p-value? Lower sample size -> higher standard deviation -> lower statistic. It says everything needed by itself.
Hi r/statistics,
I am reading up on the concept of the minimum detectable difference, and I was wondering: Let's say I wish to do an independent samples t-test to compare two groups A and B, and I find that the minimum detectable difference I can observe is k (in unstandardised units) given Ξ± = 0.05, power = 0.8, and sample size n (n = n_A + n_B, where n_A = n_B).
If I were to observe a "statistically significant" difference (p < 0.05) between the two groups that was smaller than the minimum detectable difference of k, should this scenario be interpreted as evidence of a false positive?
P.S., I'd like to say my thanks and show my appreciation to the community. Happy Christmas and new year to you.
Dust is everywhere in the universe. How large, how distant, and how fast would an object have to fly, so that we see its wake in the dust with current technology?
Not using a turn signal is also a safety issue. The technology used already available that allows the car to know if it is at a stop sign, traffic signal etc. One day, turn signals may be fully automated (and indeed self driving).
But right now, at the very least, as a safety aid, the car should signal that you made an unsafe driving maneuver by turning without signaling and it should beep at you just the way it does when you try to drive without a seat belt. Not continuously, just 2 or 3 beeps once the turn is complete.
I've got a two way right hand drive train network with the tracks placed on a single foundation but just far enough apart that trains going in opposite directions don't collide.
But, I think the tracks are too close for the block signals to work and instead they give Signal Loops onto itself errors. The screen shots below are of a straight bit of track with three signals (2 blocks).
All three blocks have Signal loop errors
If there wasn't a distance issue I'd expect 1 and 2 to be green but 3 could throw an error depending on how the rest of the track was set up.
Moving the middle signal out to the right 1 foundation, then clears the error from the second block.
Second block moved over a bit.
So it looks like if any part of the block is within 0.5(?) foundations of another line, it thinks it is the same line and causes a loop error?
Most of my T-Junctions are based on the same single foundation spacing, so this causes even more issues.
Has anyone else come across this and worked out how/if it can be fixed or what the minimum spacing should be for lines going in different directions?
This is the best tl;dr I could make, original reduced by 77%. (I'm a bot)
> Similar GPS disruptions have been reported in recent years around the Black Sea, along Russia's borders with Norway and Finland, and near the Kremlin and Russian President Vladimir Putin's palace.
> According to Humphreys, the method being used by Russia appears to be a combination of jamming, in which GPS service is outright denied, and spoofing, the term for feeding GPS receivers false information.
> He said the sudden appearance of the problem in Israel could be the result of any number of changes to Russia's deployment of its transmitters, also known as jammers - either the deployment of additional transmitters, an increase in the power of them or a repositioning of one of the jammers closer to the border with Israel.
> This GPS denial of service does not affect Russian pilots taking part in the civil war in Syria, as Russia does not rely on GPS satellites for its navigation.
> Humphreys said the jamming appeared to be an effort by Russia to prevent attacks by drones that rely on GPS navigation to attack their bases and personnel, but also is a way for Moscow to demonstrate to the entire world its "Dominance in the radio spectrum."
> In addition to Russia's GPS spoofing, Israel has been accused by Syria and Arab media of carrying out electronic warfare attacks on the Syrian military, falsely triggering or knocking out its air defenses.
Summary Source | FAQ | Feedback | Top keywords: GPS^#1 Israel^#2 Russia^#3 navigation^#4 Humphreys^#5
Post found in /r/worldnews, /r/syriancivilwar and /r/N_N_N.
NOTICE: This thread is for discussing the submission topic. Please do
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Iβve seen S1 twice and decided to pick up the books. Iβm a third into The Eye of the World, and am rewatching the series again bc I have no self control. However, thereβs one thing I havenβt been able to decipher (& am yet to get there in the books). Moraine seems to be aware of Egweneβs ability to channel before she is. Even Nynayeveβs to extent. Also, Aes Sedai can sense the amount of power Logain has when they need to shield him, which makes sense.
How come is Moraine then not aware then when Rand channels throughout the season, as we find out heβs been doing it towards the end? I know women canβt see men channeling, does that also mean they canβt know/feel that a man is a channeler until they see the effects? Thanks!
>ELF/SLF/ULF radio
>Neurons emit weak radio signals across the ELF/SLF/ULF frequency bands which are detectable remotely.[56] There have been reports that brain-computer interfaces (BCIs) utilising these bands may be achievable, since radio energy in these frequency ranges can be absorbed by neurons.[57][58][59][60]
http://dictionary.sensagent.com/Brain_computer_interface/en-en/#ELF.2FSLF.2FULF_radio
Clicking the references in this post will not open the papers. Clicking on the references in the article will open the papers. If the papers don't open, use a search engine to find them and cite the URL in a comment.
>56 Existence of Electromagnetic Radiation in Humans in ELF Band, Progress In Electromagnetics Research Symposium, August 22β26, 2005
>57 On the possibility of directly accessing every human brain by electromagnetic induction of fundamental algorithms., Behavioural Neuroscience Laboratory, Laurentian University, Sudbury, Ontario, Canada.,1995 Jun
>58 Chaos control and synchronization of two neurons exposed to ELF external electric field., School of Electrical and Automation Engineering, Tianjin University, Tianjin 300072, China.,23 March 2006
Broken link. Full text of paper is at:
http://engineering.nyu.edu/mechatronics/Control_Lab/bck/VKapila/Chaotic%20Ref/Porfiri%27s/Biblio/Wang06.pdf
>59 Unidirectional synchronization of HodgkinβHuxley neurons exposed to ELF electric field., School of Electrical and Automation Engineering, Tianjin University, Tianjin 300072, China.,29 May 2007
Broken link. Paper is at:
https://www.researchgate.net/publication/243333017_Unidirectional_synchronization_of_Hodgkin-Huxley_neurons_exposed_to_ELF_electric_field
>60 Fire patterns of modified HH neuron under external sinusoidal ELF stimulus., School of Electrical and Automation Engineering, Tianjin University, Tianjin 300072, China.,5 August 2008.
Broken link. Paper is at:
https://www.sciencedirect.com/science/article/pii/S0960077908003688
Would subscribers be interested in finding current papers?
Frequencies used:
Paper #56:
>It is typical for recordings made with the loop antenna (Fig.3) that the man present is amplifying frequency components markedly near SR. In addition to this resonance, presence of the man results in appearance of other distinctive frequency peaks on frequencies in 1.3 - 4 Hz band in signal spectres, furthermore on frequency 21.2 Hz and 28.7 Hz.
>It is typical for recordings made with large ind
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