Posts filed under General (1242)

September 19, 2017

Briefly

  • During the Cold War, there were a few occasions where a nuclear war could easily have started if one person hadn’t got in the way. One of those people was Stanislav Petrov. He died this week.
  • I saw a pharmacy in Ponsonby advertising “Ultrasound bone density screening for all ages”. There’s no way screening for osteoporosis makes sense ‘for all ages’, even if it was free (which it isn’t).
  • As I’ve mentioned a few times, the UK has an independent Statistics Authority whose chair is supposed to monitor and rebuke misuses of official statistics. The chair, Sir David Norgrove, criticised Boris Johnson over the £350m “savings” from Brexit he has kept repeating. We don’t have anything similar, sadly.
  • If you’re interested in the history of data journalism, you could do worse than reading Alberto Cairo’s PhD thesis. Dr Cairo is a former data journalist, current professor of visual journalism at the University of Miami, and one of next year’s Ihaka Lecture speakers here in Auckland.
  • Janelle Shane has a blog with examples of neural networks generalising from a wide range of inputs (recipes, hamster names, craft beers). Her current post is on D&D spell names, and shows the importance of a large input set for these networks: would you prefer your character to cast “Plonting Cloud” or “Wall of Storm”?
  • Kieran Healy, of Duke University, has an online book Data Visualization for Social Science. Yes, if you think you recognise the name, it’s him.
  • The American Statistical Association and the New York Times are partnering in a new monthly feature, “What’s Going On in This Graph?”

NRL Predictions for the Preliminary Finals

Team Ratings for the Preliminary Finals

The basic method is described on my Department home page.

Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Current Rating Rating at Season Start Difference
Storm 14.43 8.49 5.90
Broncos 6.53 4.36 2.20
Raiders 4.07 9.94 -5.90
Cowboys 3.58 6.90 -3.30
Panthers 2.80 6.08 -3.30
Sharks 2.55 5.84 -3.30
Eels 1.60 -0.81 2.40
Roosters 1.34 -1.17 2.50
Dragons -0.94 -7.74 6.80
Sea Eagles -1.11 -2.98 1.90
Bulldogs -3.55 -1.34 -2.20
Wests Tigers -3.72 -3.89 0.20
Rabbitohs -3.84 -1.82 -2.00
Warriors -7.23 -6.02 -1.20
Titans -9.03 -0.98 -8.10
Knights -9.54 -16.94 7.40

 

Performance So Far

So far there have been 198 matches played, 119 of which were correctly predicted, a success rate of 60.1%.
Here are the predictions for last week’s games.

Game Date Score Prediction Correct
1 Broncos vs. Panthers Sep 15 13 – 6 7.30 TRUE
2 Eels vs. Cowboys Sep 16 16 – 24 3.30 FALSE

 

Predictions for the Preliminary Finals

Here are the predictions for the Preliminary Finals. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Game Date Winner Prediction
1 Storm vs. Broncos Sep 22 Storm 11.40
2 Roosters vs. Cowboys Sep 23 Roosters 1.30

 

Mitre 10 Cup Predictions for Round 6

Team Ratings for Round 6

The basic method is described on my Department home page.

Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Current Rating Rating at Season Start Difference
Canterbury 19.04 14.78 4.30
Wellington 8.87 -1.62 10.50
Taranaki 6.27 7.04 -0.80
North Harbour 5.62 -1.27 6.90
Tasman 4.82 9.54 -4.70
Otago 4.03 -0.34 4.40
Counties Manukau -1.13 5.70 -6.80
Manawatu -2.01 -3.59 1.60
Auckland -2.34 6.11 -8.40
Waikato -2.59 -0.26 -2.30
Northland -4.38 -12.37 8.00
Bay of Plenty -4.61 -3.98 -0.60
Hawke’s Bay -13.56 -5.85 -7.70
Southland -20.62 -16.50 -4.10

Performance So Far

So far there have been 38 matches played, 24 of which were correctly predicted, a success rate of 63.2%.
Here are the predictions for last week’s games.

Game Date Score Prediction Correct
1 Canterbury vs. Counties Manukau Sep 13 78 – 5 20.80 TRUE
2 Northland vs. North Harbour Sep 14 22 – 31 -5.40 TRUE
3 Southland vs. Auckland Sep 15 17 – 27 -15.20 TRUE
4 Taranaki vs. Bay of Plenty Sep 15 29 – 7 13.30 TRUE
5 Waikato vs. Manawatu Sep 16 10 – 23 7.00 FALSE
6 Otago vs. Tasman Sep 16 27 – 29 4.40 FALSE
7 Counties Manukau vs. Hawke’s Bay Sep 17 33 – 14 20.60 TRUE
8 Wellington vs. Canterbury Sep 17 60 – 14 -12.90 FALSE

 

Predictions for Round 6

Here are the predictions for Round 6. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Game Date Winner Prediction
1 Bay of Plenty vs. Southland Sep 20 Bay of Plenty 20.00
2 Otago vs. Auckland Sep 21 Otago 10.40
3 Manawatu vs. Northland Sep 22 Manawatu 6.40
4 North Harbour vs. Canterbury Sep 23 Canterbury -9.40
5 Waikato vs. Wellington Sep 23 Wellington -7.50
6 Hawke’s Bay vs. Taranaki Sep 23 Taranaki -15.80
7 Bay of Plenty vs. Counties Manukau Sep 24 Bay of Plenty 0.50
8 Tasman vs. Southland Sep 24 Tasman 29.40

 

Currie Cup Predictions for Round 11

Team Ratings for Round 11

The basic method is described on my Department home page.

Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Current Rating Rating at Season Start Difference
Sharks 4.99 2.15 2.80
Western Province 3.46 3.30 0.20
Cheetahs 3.23 4.33 -1.10
Lions 3.02 7.41 -4.40
Blue Bulls 0.47 2.32 -1.90
Pumas -7.01 -10.63 3.60
Griquas -10.91 -11.62 0.70

 

Performance So Far

So far there have been 30 matches played, 20 of which were correctly predicted, a success rate of 66.7%.
Here are the predictions for last week’s games.

Game Date Score Prediction Correct
1 Pumas vs. Western Province Sep 15 22 – 12 -7.10 FALSE
2 Griquas vs. Sharks Sep 16 22 – 40 -10.10 TRUE
3 Lions vs. Blue Bulls Sep 16 36 – 33 7.80 TRUE

 

Predictions for Round 11

Here are the predictions for Round 11. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Game Date Winner Prediction
1 Sharks vs. Blue Bulls Sep 23 Sharks 9.00
2 Western Province vs. Griquas Sep 23 Western Province 18.90
3 Cheetahs vs. Pumas Sep 23 Cheetahs 14.70

 

September 18, 2017

But probably not

Q: Did you see icecream for breakfast may improve mental performance?

icecream

A: Pigs may fly

Q: But it’s a STUDY

A: That’s actually one of the questions left unresolved.

Q: Just follow the link. The International Business Times links to their source.

A: That link is to a Japanese news site. And it’s 404.

Q: Already? The tweet was just from this weekend.

A: The story is from November last year.

Q: But there’s a professor! Isn’t he real? Can’t you look at his publications.

A: Yes, he’s real. And he has publications. And they aren’t about icecream for breakfast.

Q: Back to the icecream. It could still be true, even if the data aren’t published, right?

A: Sure. In fact there’s a fair chance that, compared to no breakfast, icecream could improve mental performance.

Q: The comparison was to not eating anything?

A: It was compared to a glass of cold water.

Q: So, what does this tell us?

A: 2017 must be a slow news year.

September 17, 2017

Polls that aren’t any use

bogus-pie

From last week in the Herald: 73.6 per cent of landlords plan rent rises if Labour wins. It’s been a while since I noticed a bogus-poll headline, but they keep coming back.

This time there are two independent reasons this number is meaningless.  First, it’s a self-selected survey — a bogus poll.  You can think of self-selected surveys as a type of petition: they don’t tell you anything useful about the people who didn’t respond, so the results are only interesting if the absolute number responding in a particular category is surprisingly high.  In this case, it’s 73.6% of 816 landlords. According to an OIA request in 2015,  there are more than 120,000 landlords in NZ, so we’re looking at a ‘yes’ response from less than half a percent of them.

Second, there’s an important distinction in polling questions to worry about.  If a nice pollster calls you up one evening and asks who you’re voting for, there’s no particular reason to say anything other than the truth.  The truth is the strongest possible signal of your political affiliation.  If a survey asks “will you raise rents if Labour gets in and raises costs?”,  it’s fairly natural to say “yes” as a sign that you don’t support Labour, whether it’s true or not. There’s no cost to saying “yes”, but if you’re currently setting rents at what you think is the right level, there is a cost to raising them.

Those of you who do arithmetic compulsively will have noticed another, more minor, problem with the headline.  There is no number of votes out of 816 that rounds correctly to 73.6%:  600/816 is 73.52941%, ie, 73.5% and 601/816 is 73.65196, ie, 73.7%.  And, of course, headlining the results of any poll, even a good one, to the nearest tenth of a percentage point is silly.

September 13, 2017

Thresholds and discards, again

There are competing explanations out there about what happens to votes for a party that doesn’t reach the 5%/1 electorate threshold.  This post is about why I don’t like one of them.

People will say (such as on NZ Morning Report this morning) that your votes are reallocated to other parties.  In some voting systems, such as the STV we use for local government elections, reallocating votes is a thing. Your voting paper literally (or virtually) starts off in one party’s pile and is moved to a different party’s pile.

That’s not what happens with the party votes for Parliament.  If the Greens don’t make 5%, party votes for the Greens are not used in allocating List seats.  It’s exactly as if those voters hadn’t cast a party vote, which I think is a simple enough explanation to use.

Now, in the vast majority of cases the result will be the same as if the votes had been reallocated in proportion — unless something weird like a tie happens at some stage in the counting — but one of the explanations is what happens and the other one isn’t.

If you think the two explanations convey the same meaning, you shouldn’t object to using the one that’s actually correct. And if you think they convey different meanings, you definitely shouldn’t object to using the one that’s actually correct.

 

September 12, 2017

NRL Predictions for Finals Week 2

Team Ratings for Finals Week 2

The basic method is described on my Department home page.

Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Current Rating Rating at Season Start Difference
Storm 14.43 8.49 5.90
Broncos 6.56 4.36 2.20
Raiders 4.07 9.94 -5.90
Panthers 2.77 6.08 -3.30
Cowboys 2.68 6.90 -4.20
Sharks 2.55 5.84 -3.30
Eels 2.51 -0.81 3.30
Roosters 1.34 -1.17 2.50
Dragons -0.94 -7.74 6.80
Sea Eagles -1.11 -2.98 1.90
Bulldogs -3.55 -1.34 -2.20
Wests Tigers -3.72 -3.89 0.20
Rabbitohs -3.84 -1.82 -2.00
Warriors -7.23 -6.02 -1.20
Titans -9.03 -0.98 -8.10
Knights -9.54 -16.94 7.40

 

Performance So Far

So far there have been 196 matches played, 118 of which were correctly predicted, a success rate of 60.2%.
Here are the predictions for last week’s games.

Game Date Score Prediction Correct
1 Roosters vs. Broncos Sep 08 24 – 22 -2.50 FALSE
2 Storm vs. Eels Sep 09 18 – 16 17.90 TRUE
3 Sea Eagles vs. Panthers Sep 09 10 – 22 -2.30 TRUE
4 Sharks vs. Cowboys Sep 10 14 – 15 4.20 FALSE

 

Predictions for Finals Week 2

Here are the predictions for Finals Week 2. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Game Date Winner Prediction
1 Broncos vs. Panthers Sep 15 Broncos 7.30
2 Eels vs. Cowboys Sep 16 Eels 3.30

 

Mitre 10 Cup Predictions for Round 5

Team Ratings for Round 5

The basic method is described on my Department home page.

Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Current Rating Rating at Season Start Difference
Canterbury 20.07 14.78 5.30
Taranaki 5.49 7.04 -1.50
North Harbour 5.30 -1.27 6.60
Otago 4.60 -0.34 4.90
Tasman 4.24 9.54 -5.30
Counties Manukau 3.29 5.70 -2.40
Wellington 3.14 -1.62 4.80
Waikato -0.79 -0.26 -0.50
Auckland -1.87 6.11 -8.00
Manawatu -3.81 -3.59 -0.20
Bay of Plenty -3.83 -3.98 0.10
Northland -4.06 -12.37 8.30
Hawke’s Bay -13.28 -5.85 -7.40
Southland -21.09 -16.50 -4.60

 

Performance So Far

So far there have been 30 matches played, 19 of which were correctly predicted, a success rate of 63.3%.
Here are the predictions for last week’s games.

Game Date Score Prediction Correct
1 Wellington vs. Hawke’s Bay Sep 06 40 – 27 17.70 TRUE
2 Counties Manukau vs. North Harbour Sep 07 18 – 27 4.40 FALSE
3 Canterbury vs. Southland Sep 08 78 – 20 42.30 TRUE
4 Manawatu vs. Bay of Plenty Sep 08 17 – 20 5.60 FALSE
5 Auckland vs. Taranaki Sep 09 38 – 49 -1.70 TRUE
6 Northland vs. Waikato Sep 09 37 – 7 -5.70 FALSE
7 Tasman vs. Wellington Sep 10 37 – 35 5.40 TRUE
8 Hawke’s Bay vs. Otago Sep 10 21 – 64 -7.90 TRUE

 

Predictions for Round 5

Here are the predictions for Round 5. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Game Date Winner Prediction
1 Canterbury vs. Counties Manukau Sep 13 Canterbury 20.80
2 Northland vs. North Harbour Sep 14 North Harbour -5.40
3 Southland vs. Auckland Sep 15 Auckland -15.20
4 Taranaki vs. Bay of Plenty Sep 15 Taranaki 13.30
5 Waikato vs. Manawatu Sep 16 Waikato 7.00
6 Otago vs. Tasman Sep 16 Otago 4.40
7 Counties Manukau vs. Hawke’s Bay Sep 17 Counties Manukau 20.60
8 Wellington vs. Canterbury Sep 17 Canterbury -12.90

 

Currie Cup Predictions for Round 10

Team Ratings for Round 10

The basic method is described on my Department home page.

Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Current Rating Rating at Season Start Difference
Sharks 4.36 2.15 2.20
Western Province 4.04 3.30 0.70
Lions 3.41 7.41 -4.00
Cheetahs 3.23 4.33 -1.10
Blue Bulls 0.09 2.32 -2.20
Pumas -7.60 -10.63 3.00
Griquas -10.29 -11.62 1.30

 

Performance So Far

So far there have been 27 matches played, 18 of which were correctly predicted, a success rate of 66.7%.
Here are the predictions for last week’s games.

Game Date Score Prediction Correct
1 Griquas vs. Lions Sep 08 17 – 34 -8.50 TRUE
2 Western Province vs. Cheetahs Sep 09 57 – 14 3.20 TRUE
3 Pumas vs. Sharks Sep 09 25 – 27 -8.50 TRUE

 

Predictions for Round 10

Here are the predictions for Round 10. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Game Date Winner Prediction
1 Pumas vs. Western Province Sep 15 Western Province -7.10
2 Griquas vs. Sharks Sep 16 Sharks -10.10
3 Lions vs. Blue Bulls Sep 16 Lions 7.80