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Wednesday, January 13, 2010

The National…To tick or not to tick…BC Scotties 8th End

Greetings and Happy New Year to all. Many items to dig into this month so let’s get right to it….

1. Grand Slam - Swiss Chalet National

Semi-Final: Brad Gushue vs. Glenn Howard
A rematch of the 2007 Brier final.  That game included an interesting decision by Gushue which I analyzed here

One of the more interesting decisions in this rematch was the 1st End. Tied (naturally) without hammer, Gushue was faced with an option on his first rock to be aggressive and attempt a steal but instead chose to peel out the Howard stone protecting his rock in the four foot. This shot call forced Howard to a single rather than giving Gushue a chance at a possible steal.

Gushue is Red

Down 1 with hammer and 7 ends remaining WP = 47%.
Down 2 with hammer and 7 ends remaining WP = 26%

Assuming the most Howard will take is two, how often does he need to estimate a deuce occurs for the Gushue call to be correct?

We will assume that if Gushue peels Howard will always take 1. Chance of a blank is assumed negligible.

x = Gushue steal
y = Howard scores 1
z = Howard scores 2
.47 = .53x + .47y +.26z

Simply looking at the equation, if x =0 than the correct decision is to peel. Let’s choose x as 25%.
.47= (.25)(.53)+(1-z-.25)(.47)+z(.26)
Solving for z = 7%

Would appear the decision which at first seemed conservative is very prudent, given the estimates we have chosen. Hard to believe that with the Gushue rock behind the button that Howard will fail to prevent a steal at least 75% with two rocks to come. Even if Howard never scores a deuce and Gushue steals 50% of the time, he only increases his WP from 47% to 50%.

Finals: Brad Gushue vs. Randy Ferbey

3rd End
Game is tied, Ferbey has hammer. Gushue places a centre guard with the first stone. Marcel places his stone in a high position, biting the eight foot. Gushue elects to play a runback on his own rock, which he is entitled to do under the 4-rock Free Guard Zone rules. Not a play we see very often. Teams commonly play a corner freeze regardless of the placement of this stone. I think this type of play could be used more often.

What is interesting is, tied with 6 ends remaining, a team chooses to place a guard without hammer – while two ends previously they commonly put it in the rings.

This leads to a question a poster on CurlingZone asked: “If you have hammer in the first end of an eight end game and your opponent places a rock in the rings, should you hit with desire to blank the end and have hammer in the second?”

The odds do not change from 8 ends to 7 ends remaining. Beginning eac end, probable outcome for Tied with hammer WP= 61%, one down with hammer WP=43% and down two with hammer WP=26%.  These ends are considered the Early Game, which I explained in this past article:

Possible reasons for choosing this play:
  • If your opponent is stronger you may want to shorten the game.
  • You want to conserve time by playing a quick end early
  • You are unfamiliar with ice and/or rocks
There may be other considerations I haven’t addressed. I prefer aggressive play as outlined in a previous article:

However, taking into account other considerations could lead a team to the decision to play an open end for a blank. As always, understanding the numbers is a first step but situational analysis must always be considered as well.

4th End
Ferbey is up 2-1 without hammer. It is Nedohin’s last rock of the end.

After much discussion, the Ferbey rink decided to play a freeze to shot stone in the four foot, forcing Gushue to make a difficult shot for multiple score or possibly even steal. Dave makes a great shot but not quite perfect and Gushue is left with a run back for three, which he makes.
Gushue is Red

Gushue is Red

At one stage, the Ferbey team discussed hitting the half open Gushue rock in the eight foot, conceding a deuce. Randy mentioned he was unsure of the ice, though I ‘m surprised given it’s the 4th end and the final game of the event. The question I had is, if they could be assured of conceding a deuce, how often does Dave’s rock need to be perfect to make the shot call they attempted?

When 1 down with hammer and 4 ends remaining WP = 41%

If Ferbey attempts the freeze, 4 outcomes are possible: steal, Gushue takes one, two or three. This leaves a lot of possible outcomes to examine.
WP = .79s + .62x + .41y + .21z

Let’s examine extreme case where Gushue scores three 60% of the time, deuce 20% and 10% forced to one and 10% a steal.
WP = 35%
If z becomes 30% and a deuce (y) becomes 50%, WP = 41%.

It’s very likely if Nedohin’s shot curls 2-3 inches more the play for three is not even possible. I’d suggest Ferbey’s estimation of David placing the rock perfectly would lead him to believe giving up three is not likely higher than 30% and is certainly not 50%.

What we don’t know is, if Dave’s rock had been short, leaving Gushue sitting one, would Gushue simply draw for two anyway, rather than attempt the hit for three?

7th End
Tied without hammer, Ferbey has a long off centre guard and a Gushue stone in the wings. It is Nedohin’s first shot.

Gushue is Red

They could choose to play around the guard and attempt to steal or force Gushue to one at the risk of a possible deuce. They instead choose to hit and increase the likelihood of a blank, which occurs, and then need to steal in the final end to win (WP=25%).

Compare this decision with their choice to risk a difficult double for two to go one up against Howard in the Olympic Trials, rather than take a single and be tied without coming home.

Here they take a very different approach. Perhaps it was their competition, thinking the chance at a steal was better than in the previous situation. Instead it could have been the ice conditions and the length of the guard led Ferbey to believe a deuce was simply too likely. In either case, a somewhat surprising call given Ferbey’s aggressive nature. Looking at the numbers, assuming a draw attempt will result in no blank, if we assume Ferbey never steals, he will need to successfully force a single by Gushue at least 45% of the time to make it the correct decision.

2. Tied with hammer “To tick or not to tick”
I recently read Russ Howard’s book “Curl to Win”. In it, he discusses the situation of tied with hammer in the final end. His preferred strategy is to play both leads rocks into the top of the rings, allowing your opponent to place two centre guards.

I noticed this weekend that both Gushue (against Ferbey in the final) and Koe (against Murdoch in the quarterfinal) adhered to this philosophy. Ferbey, in his round robin game against Gushue chose the alternate strategy of playing tick shots to remove both guards. Interestingly, Russ’ brother Glenn used the tick strategy during the Olympic Trials against Koe.

Both Gushue and Koe won their games, but both had tense finishes in which their opponent had chances to perhaps pull out a victory.

I can appreciate Russ’ approach, but prefer the tick strategy for a few reasons, one of which he mentions in his book.

  1. If the first tick is missed, you can choose to draw around on your next shot. I believe a well placed rock has nearly as much benefit as placing two stones, and still provides an option to make the tick shot.
  2. At this level, teams should be able to succeed at the tick shot. It would surprise that top teams would not be extremely proficient at making the tick shot a high percentage of the time.
  3. If you could walk down to the end of the sheet and place the stones, what would you do?. The obvious answer is open the front of the rings by moving the guards. So if you can’t move the rocks correctly by throwing them, practice until you can.
  4. More rocks give the team behind more options.  This is a general concept that does not clearly translate to all situations, and does not have sufficient data to defend, but may have some validity in these scenarios.
I suspect over time the tick will become the more common play, but for now the “draw twice” strategy appears to have some followers.

3. BC Scotties - Kelly Scott vs. Kelly Law
Several posts on CurlingZone related to Kelly Scott’s decision to draw for a single point in the eighth end of the BC Provincial final. Rather than blank and start the 9th end 2 up with hammer, Scott chose to be three up without and two ends remaining.

The numbers actually indicate the decision is equal, a team’s WP =7% whether they are down three with or two without hammer. I would support either decision as it was made based on any number of other factors such as ice conditions or opponent.

To those posters who state that Scott made a horrible decision and it almost cost her the game due the outcome which almost occurred in the 9th end: you are wrong. Basing how a single end plays out and what occurs is irrelevant to how a decision is reached beforehand. Even if you argued Kelly made a wrong decision that her competition and/or conditions should have led her to blank, it simply is not a big enough “mistake” in that case to have a substantial impact. For example, if she was 100% wrong (and she wasn’t), Law’s chances only increase to 14%, still a Dominant position for Scott.

Congratulations to all the Scotties Provincial Winners. Also, congratulations once again to the Lobel Team for gaining a third straight trip to the Provincials in Ontario. 

Until next time, remember to keep your numbers in mind before placing your broom.

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