band of inaction balances the two costs, and turns out to be equivalent to a confidence interval. This makes the band of inaction describable as a two-sided hypothesis test-in other words IE is an “as if theory of optimal decision making. In view of what we consider to be reasonable implications and foundations, our modelling strategy is an extension of the IE work on central banking by Henckel et al. (2011). We treat beliefs about the central bank inflation target as a null belief in a hypothesis test, where Ho corresponds to the official target value. In the case of the ECB we will treat this value as 2 percent. We posit an IE Phillips curve of the following form: T = BH, + (1 – B)E[n] + £ xXi + ŋ. i (1) Aggregate inflation a depends on the inferential expectations of price setters, a fraction ß of whom fail to reject Họ and a fraction 1- B of whom reject Ho and work out the rational expectation of inflation, based on (1). The variable Ho is the value inflation takes under the null, which in our analysis is 2 percent for the ECB. The X; are other explanators, variables like the output gap, which are zero in the steady-state. The estimation error n is assumed to be i.i.d. We can simplify the above equation by noting that, when agents adopt rational expectations, they can use (1) to solve for E[T]: Σ E[7] = BHo + (1 – B)E[n] + £„X; E [7] = H, + i which can be substituted into (1) to obtain the IE Phillips curve: Σ T = Ho + Xị + ŋ. (2) Eq. (2) is noteworthy because the marginal impacts of the X{'s depend upon the proportion of agents that are anchored onto Họ. The more they abandon the inflation target (the lower ß) the more they must rely on other variables for their expectations, which magnifies their marginal impacts. Thus, a testable implication of the IE Phillips curve is that all the coefficients on the X¡'s will rise by the same proportion when agents abandon the null. It is a noteworthy feature of many crises that previously unimportant variables can become more important, and (2) is a new (and testable) model of why this might be so.º 3.2. Steady-State B

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Chapter8: Sequences, Series, And Probability
Section8.7: Probability
Problem 58E: What is meant by the sample space of an experiment?
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Hi there, can you please help me provide a full derivation of equations (1) to (2). I can use equation (1) as the starting point and assume E(X)=X.

I've attached a snippet of the two equations :)

Please help me with the process of the derivations and the steps! Thanks!

 

band of inaction balances the two costs, and turns out to be equivalent to a confidence interval. This makes the band of inaction
describable as a two-sided hypothesis test-in other words IE is an “as if theory of optimal decision making.
In view of what we consider to be reasonable implications and foundations, our modelling strategy is an extension of the IE work
on central banking by Henckel et al. (2011). We treat beliefs about the central bank inflation target as a null belief in a hypothesis
test, where Ho corresponds to the official target value. In the case of the ECB we will treat this value as 2 percent.
We posit an IE Phillips curve of the following form:
8
n = BH, + (1 – B)E[n] + Z %X; + ŋ.
(1)
Aggregate inflation a depends on the inferential expectations of price setters, a fraction ß of whom fail to reject Họ and a fraction
1- B of whom reject Ho and work out the rational expectation of inflation, based on (1). The variable Ho is the value inflation takes
under the null, which in our analysis is 2 percent for the ECB. The X; are other explanators, variables like the output gap, which are
zero in the steady-state. The estimation error 7 is assumed to be i.i.d. We can simplify the above equation by noting that, when agents
adopt rational expectations, they can use (1) to solve for E[n]:
E[n] = BH0 + (1 – B)E[n] + > ,X;
Σ
E [z] = Ho + EX,
i
which can be substituted into (1) to obtain the IE Phillips curve:
T = Ho +
i + ŋ.
i
(2)
Eq. (2) is noteworthy because the marginal impacts of the X{s depend upon the proportion of agents that are anchored onto Ho.
The more they abandon the inflation target (the lower B) the more they must rely on other variables for their expectations, which
magnifies their marginal impacts. Thus, a testable implication of the IE Phillips curve is that all the coefficients on the X{'s will rise by
the same proportion when agents abandon the null. It is a noteworthy feature of many crises that previously unimportant variables
can become more important, and (2) is a new (and testable) model of why this might be so.
3.2. Steady-State ß
A key parameter in (2) is ß and we now characterize it both in, and out of, the steady-state. By steady-state we mean that the
equation error and the X{'s in (2) are zero, which implies 7 = H, for any value of ß; that is, the value of inflation under the null
hypothesis is the rational expectation. We can now work out the steady-state value of ß knowing that any value of ß is consistent with
a steady-state for a, and that the null belief about inflation is true in the steady-state.
Because the population of agents forming inflation expectations is heterogeneous, we assume that agents take an i.i.d. draw of a
test size a from a common density for a. For example, a group of 'classical statisticians" might draw a = 0.05 and 0.10 with equal
probability. Since Ho is true in the steady-state, then ß must be the proportion of agents believing the null under Ho, which is 1 – a if
a is a single number and 1 – E[a] if a has a distribution.10
All that is required to calculate steady-state ß is the mean of the density of a. For example, our "classical statisticians" have
E[a] = 0.05/2 + 0.10/2 and hence B = 1 – 0.075 = 0.925. However, based on the wide range of a's elicited in Menzies and
Zizzo (2012) and Henckel et al. (2018) we here assume a is uniform across support (0,1) implying E[a] = 0.5 and ß = 0.5.
When we later run a regression like (2) it will be impossible to separately identify the y's and ß. However, if we assume the model
is in a steady-state prior to the shock (the 2008 crisis) we can infer both y and, if we attribute any rise in the estimated coefficient to ß,
Transcribed Image Text:band of inaction balances the two costs, and turns out to be equivalent to a confidence interval. This makes the band of inaction describable as a two-sided hypothesis test-in other words IE is an “as if theory of optimal decision making. In view of what we consider to be reasonable implications and foundations, our modelling strategy is an extension of the IE work on central banking by Henckel et al. (2011). We treat beliefs about the central bank inflation target as a null belief in a hypothesis test, where Ho corresponds to the official target value. In the case of the ECB we will treat this value as 2 percent. We posit an IE Phillips curve of the following form: 8 n = BH, + (1 – B)E[n] + Z %X; + ŋ. (1) Aggregate inflation a depends on the inferential expectations of price setters, a fraction ß of whom fail to reject Họ and a fraction 1- B of whom reject Ho and work out the rational expectation of inflation, based on (1). The variable Ho is the value inflation takes under the null, which in our analysis is 2 percent for the ECB. The X; are other explanators, variables like the output gap, which are zero in the steady-state. The estimation error 7 is assumed to be i.i.d. We can simplify the above equation by noting that, when agents adopt rational expectations, they can use (1) to solve for E[n]: E[n] = BH0 + (1 – B)E[n] + > ,X; Σ E [z] = Ho + EX, i which can be substituted into (1) to obtain the IE Phillips curve: T = Ho + i + ŋ. i (2) Eq. (2) is noteworthy because the marginal impacts of the X{s depend upon the proportion of agents that are anchored onto Ho. The more they abandon the inflation target (the lower B) the more they must rely on other variables for their expectations, which magnifies their marginal impacts. Thus, a testable implication of the IE Phillips curve is that all the coefficients on the X{'s will rise by the same proportion when agents abandon the null. It is a noteworthy feature of many crises that previously unimportant variables can become more important, and (2) is a new (and testable) model of why this might be so. 3.2. Steady-State ß A key parameter in (2) is ß and we now characterize it both in, and out of, the steady-state. By steady-state we mean that the equation error and the X{'s in (2) are zero, which implies 7 = H, for any value of ß; that is, the value of inflation under the null hypothesis is the rational expectation. We can now work out the steady-state value of ß knowing that any value of ß is consistent with a steady-state for a, and that the null belief about inflation is true in the steady-state. Because the population of agents forming inflation expectations is heterogeneous, we assume that agents take an i.i.d. draw of a test size a from a common density for a. For example, a group of 'classical statisticians" might draw a = 0.05 and 0.10 with equal probability. Since Ho is true in the steady-state, then ß must be the proportion of agents believing the null under Ho, which is 1 – a if a is a single number and 1 – E[a] if a has a distribution.10 All that is required to calculate steady-state ß is the mean of the density of a. For example, our "classical statisticians" have E[a] = 0.05/2 + 0.10/2 and hence B = 1 – 0.075 = 0.925. However, based on the wide range of a's elicited in Menzies and Zizzo (2012) and Henckel et al. (2018) we here assume a is uniform across support (0,1) implying E[a] = 0.5 and ß = 0.5. When we later run a regression like (2) it will be impossible to separately identify the y's and ß. However, if we assume the model is in a steady-state prior to the shock (the 2008 crisis) we can infer both y and, if we attribute any rise in the estimated coefficient to ß,
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