**What's your current API key?**

**Event Study about rating changes**

Dear Event study tools,

I am studying the rating changes effect on stock price, at the moment I use the market model to calculate the abnormal returns in the event window for each rating change for each company in the sample. I have this data but I don't understand how I can aggregate them into the Average abnormal returns and later into the CAAR, also I am a concerned about how to determine the standard deviation for T- test.

Many thanks in advance for your kind attention

**t-test fpr CAAR**

Dear Dr. Müller,

for the t-test (mentioned on eventstudytools - parametric test statistics number 1) it is possible to test H0:ARi,t=0 and H0:CARi=0.

For my study I am using the paper of MacKinlay (1997). On page 24, formula (20), he used a test of which I thougt that it is a t-test for CAAR. Dymke (2010) used this formula of MacKinlay on page 77 too. But on page 79 he talks about the parametric test of Brown/Warner (1985).

I am confused and need some help.

Thanks in advance.

Daniel

**Test statistic formula for CARs**

Hi,

I am happy to use information you provide on your great website to do my event study.

I was wondering about the formula of the standard deviation of CARs for each firm. S2CAR = L2*S2*ARi.

What is meant by L2?

Is it the number of days of the event period?

Or is it the number of day of the subperiod of my event in case i want to check the significance of t-3 - t+3 for each firm (=7)??

Is L2 multipled by S2*ARi or does it mean that I should use S2*ARi of the event window?

I would be very happy to receive an answer?

Best Wolfgang

**Z -statistic in Corrado Test**

Dear Mr. Mϋller

I’m conducting event study in Indonesian market for my bachelor thesis. Following Sudeck & Iatridis (2014), I will use Patell test and Corrado test to test my hypothesis. I want to ask you several questions:

1. Is it okay not to conduct normality test of my data? I mean, I understand that Patell test is used in case the data are normal, while Corrado test is used when my data are not normally distributed. But I confused, should I just do both test without doing normality test?

2. When I look at Campbell & Minguez-Vera (2010), we will find Z-statistic at the end of Corrado test calculation. Do test its significance, can I use Z-table for comparison? Or should I compare Z-statistic of Corrado test with another statistic table?

Please help me. Thank you very much.

**Event Study**

Sehr geehrter Herr Müller,

mein Name ist Sandip Deol und ich stúdiere Internatrional Finance. Zurzeit habe ich ein Projekt am laufen. In diesem Projekt geht es um Auswertungen von Artikeln die sich auf die Weltwirtschaftskrisen beziehen. Wir bewerten die Artikeln nach einer Skalar. Das Problem vor dem ich stehe ist, dass ich nicht weiß, wie ich meine ausgewerteten Artikeln mit in meine Event Study mit hineinbeziehen kann. Da ich die Dax Kurse mit betrachte, arbeite ich eher mit den Kursen als wie mit meiner Auswertung. Meine Hypothese lautet, ob Artikel Veröffentlichungen eine Weltwirtschaftskrise hervorsehen kann. Könnten Sie mit diesbezüglich helfen ? Könnte ich Sie telefonisch erreichen?

ich wäre Ihnen sehr dankbar dafür.

Mit freundlichen Grüßen

Sandip Deol

**VOLUME EVENT STUDY**

I would like to use EventStudyTools for volume eventstudy.

The market data required "mean of log percentage of trading volume of index".

Could you advise me how to derived the value from raw data "volume of index".

thank you

**Should I use Market Model( OLS ) or Market Model ( Garch)?**

Dear Professor,

I conduct ARCH effect tests on the firms in my samples, and find that around half of the firms has significant ARCH effect, while the other half has no ARCH effect.

I wonder which model I should use. The Market Model or the GARCH Model?

Best wishes,

Chelsea

**T Value for abnormal return**

Sir

My event day is different but firms are from different industry so can i divide abnormal return by Standard error for finding the t value or Is there any other method.

**Standardized abnormal return**

Dear Mr Muller,

I'm conducting an event study analysis and I would like to use the BPM test. My question is how can I calculate the sARi,t (standard deviation)? Is there one for every company at every t?

I hope you can help me and solve my doubt.

Thank you very much.

Best regards,

Francesco